Adhesive sheet

ABSTRACT

Provided is a pressure sensitive adhesive sheet containing, on a substrate or a release material, a resin layer formed of a multilayer structure of three or more layers including a fine particle-containing layer that contains fine particles in an amount of 15% by mass or more, at least a surface (α) of the resin layer being opposite to the side thereof on which the substrate or the release material is provided having pressure sensitive adhesiveness, wherein the fine particle-containing layer is formed not as the outermost layer of the resin layer, and one or more concave portions exist on the surface (α) and the shapes of the one or more concave portions have irregular shapes. When attached to an adherend, the pressure sensitive adhesive sheet can exhibit excellent air escape property of readily removing air accumulation which may be formed, good blister resistance and good pressure sensitive adhesion characteristics.

TECHNICAL FIELD

The present invention relates to a pressure sensitive adhesive sheet.

BACKGROUND ART

A general pressure sensitive adhesive sheet is constituted by asubstrate, a pressure sensitive adhesive layer formed on the substrate,and a release material provided on the pressure sensitive adhesive layerdepending on necessity, and in use, after removing the release materialin the case where the release material is provided, the general pressuresensitive adhesive sheet is attached to an adherend by making thepressure sensitive adhesive layer into contact therewith.

A pressure sensitive adhesive sheet having a large attaching area, whichmay be used for identification or decoration, masking for painting,surface protection of a metal plate or the like, and the like, has aproblem that on attaching the sheet to an adherend, air accumulation isliable to occur between the pressure sensitive adhesive layer and theadherend, and the portion with the air accumulation is recognized as“blister”, so as to prevent the pressure sensitive adhesive sheet frombeing attached cleanly to the adherend.

For solving the problem, for example, PTL 1 describes a pressuresensitive adhesive sheet having grooves with a particular shape that aredisposed artificially in a prescribed pattern on the surface of thepressure sensitive adhesive layer by making a release material having afine emboss pattern into contact with the surface of the pressuresensitive adhesive layer.

There is described that, by using the pressure sensitive adhesive sheet,it is possible to escape the “air accumulation” formed on attaching toan adherend, to the exterior through the grooves formed artificially onthe surface of the pressure sensitive adhesive layer.

CITATION LIST Patent Literature

PTL 1: JP 2001-507732 A

SUMMARY OF INVENTION Technical Problem

However, the pressure sensitive adhesive sheet having a pressuresensitive adhesive layer having grooves with a particular shape disposedin a prescribed pattern, as shown in PTL 1, has a problem that when thewidth of the grooves is small, it is difficult to vent the air, and whenthe width of the grooves is large, not only the surface of the substrateis dented to deteriorate the appearance, but also the pressure sensitiveadhesive strength is lowered.

In the pressure sensitive adhesive sheet, the grooves disposed in aprescribed pattern deteriorate the pressure sensitive adhesive strengthlocally in the portion having the grooves disposed, and after attachingthe pressure sensitive adhesive sheet to an adherend, there is apossibility that the sheet is detached therefrom in the portion.

In the case where the pressure sensitive adhesive sheet is attached toan adherend and then peeled again therefrom, there is a possibility ofadhesive deposits remaining on the adherend depending on the peelingdirection of the pressure sensitive adhesive sheet since the pressuresensitive adhesion characteristics of the pressure sensitive adhesivesheet varies locally. For example, in the case where the pressuresensitive adhesive sheet having the pressure sensitive adhesive layerwherein the grooves of a lattice pattern is disposed is peeledobliquely, there is a possibility of adhesive deposits remaining on theadherend.

Furthermore, in the case where the pressure sensitive adhesive sheet ispunched out, there is a possibility that the disposition pattern of thegrooves overlaps the punching pattern. In this case, the cutting depthmay fluctuate to provide a problem that a cut line cannot be suitablyformed in the pressure sensitive adhesive sheet.

In general, such a process step of forming a trigger for peeling inorder to facilitate the peeling of the release material (i.e., aso-called back slit) by only cutting a release material provided on thepressure sensitive adhesive sheet may be performed. In the case wherethe above step is performed, it is the general procedure that therelease material is once peeled off from the pressure sensitive adhesivesheet, and after putting notches in the release material, the releasematerial and the pressure sensitive adhesive layer of the pressuresensitive adhesive sheet are again laminated with each other.

In the pressure sensitive adhesive sheet described in PTL 1, however,due to the use of an embossed liner as the release material, it isnecessary to provide a separate release material that is not embossed.Because, it is difficult to follow to the emboss pattern of the releasematerial when laminating again the release material and the pressuresensitive adhesive layer.

In PTL 1, further, for forming a minute structure in the pressuresensitive adhesive layer, such a method is used that the pressuresensitive adhesive layer is once formed by coating a pressure sensitiveadhesive on the embossed liner, and then the pressure sensitive adhesivelayer and a substrate are laminated (i e, a so-called transfer coatingmethod). However, in the case where a substrate having a surface withlow polarity, such as a polyolefin substrate, is used, sufficientadhesiveness cannot be obtained between the substrate and the pressuresensitive adhesive layer by the method.

Moreover, as different from a release material formed of paper, arelease material formed of a resin film is difficult to form a fineemboss pattern to a pressure sensitive adhesive layer.

In addition, the pressure sensitive adhesive sheet described in PTL 1 isinferior in blister resistance, and thus has a problem that blister isliable to occur in the case where the sheet is used at a hightemperature.

An object of the present invention is to provide a pressure sensitiveadhesive sheet that has an excellent air escape property capable ofeasily removing air accumulation that may be formed on attaching to anadherend, and is excellent in blister resistance and pressure sensitiveadhesion characteristics.

Solution to Problem

The present inventors have found that a pressure sensitive pressuresensitive adhesive sheet having one or more concave portions existing inthe surface of a resin layer formed of a multilayer structure containinga fine particle-containing layer, in which the shapes of the one or moreconcave portions have irregular shapes, can solve the above-mentionedproblems, and thereby have completed the present invention.

Specifically, the present invention provides the following [1] to [18].

[1] A pressure sensitive adhesive sheet containing, on a substrate or arelease material, a resin layer formed of a multilayer structure ofthree or more layers including a fine particle-containing layer thatcontains fine particles in an amount of 15% by mass or more, at least asurface (α) of the resin layer being opposite to the side thereof onwhich the substrate or the release material is provided having pressuresensitive adhesiveness,

wherein the fine particle-containing layer is formed not as theoutermost layer of the resin layer, and

one or more concave portions exist on the surface (α) and the shapes ofthe one or more concave portion have irregular shapes.

[2] The pressure sensitive adhesive sheet according to the above [1],wherein the one or more concave portions are formed throughself-formation of the resin layer.[3] The pressure sensitive adhesive sheet according to the above [1] or[2], wherein, in the cross section in the thickness direction of theresin layer, the boundary between the fine particle-containing layer andthe other layer is not parallel to the horizontal plane of the substrateor the release material.[4] The pressure sensitive adhesive sheet according to any one of theabove [1] to [3], wherein the one or more concave portions do not have apredetermined pattern.[5] The pressure sensitive adhesive sheet according to any one of theabove [1] to [4], wherein the plural concave portions exist on thesurface (α).[6] The pressure sensitive adhesive sheet according to the above [5],wherein the positions at which the plural concave portions exist have noperiodicity.[7] The pressure sensitive adhesive sheet according to any one of theabove [1] to [6], wherein the fine particle-containing layer includes,as existing therein intermittently relative to the horizontal planedirection of the substrate or the release material, a part denselycontaining fine particles and a part not containing fine particles.[8] The pressure sensitive adhesive sheet according to any one of theabove [1] to [7], wherein the fine particles are one or more selectedfrom silica particles, metal oxide particles and smectite.[9] The pressure sensitive adhesive sheet according to any one of theabove [1] to [8], wherein the volume-average secondary particle diameterof the fine particles is 50 urn or less.[10] The pressure sensitive adhesive sheet according to any one of theabove [1] to [9], wherein the irregular shapes of the one or moreconcave portions existing on the surface (α) can be visually recognizedfrom the side of the exposed surface (α) by observing with naked eyes.[11] The pressure sensitive adhesive sheet according to any one of theabove [1] to [10], wherein the other layer than the fineparticle-containing layer is formed of a composition containing a resinas a main component and having the fine particles content of less than15% by mass.[12] The pressure sensitive adhesive sheet according to any one of theabove [1] to [11], wherein the resin layer has a multilayer structureof, as laminated in this order, a layer (Xβ) mainly containing a resinpart (X), a fine particle-containing layer (Y1) containing a particlepart (Y) in an amount of 15% by mass or more, and a layer (Xα) mainlycontaining a resin part (X).[13] The pressure sensitive adhesive sheet according to the above [12],wherein the resin part (X) contains at least one or more selected from ametal chelate crosslinking agent, an epoxy crosslinking agent and anaziridine crosslinking agent.[14] The pressure sensitive adhesive sheet according to the above [12]or [13], wherein the layer (Xβ) is a layer formed of a composition (xβ)containing a resin as a main component, the layer (Y1) is a layer formedof a composition (y) containing fine particles in an amount of 15% bymass or more, and the layer (Xα) is a layer formed of a composition (xα)containing a resin as a main component.[15] A method for producing a pressure sensitive adhesive sheetaccording to any one of the above [1] to [13], which includes at leastthe following steps (1) and (2):

step (1): a step of forming a coating film (x′) formed by a composition(x) containing the resin as a main component, and a coating film (y′)formed by a composition (y) containing the fine particles in an amountof 15% by mass or more; and

step (2): a step of drying the coating film (x′) and the coating film(y′) formed in the step (1) simultaneously.

[16] A method for producing a pressure sensitive adhesive sheetaccording to the above [14], which includes at least the following steps(1A) and (2A):

step (1A): a step of forming, on a substrate or a release material, acoating film (xβ′) formed by the composition (xβ) containing the resinas a main component, a coating film (y′) formed by the composition (y)containing the fine particles in an amount of 15% by mass or more and acoating film (xα′) formed by the composition (xα) containing the resinas a main component, by laminating in this order; and

step (2A): a step of drying the coating film (xβ′), the coating film(y′) and the coating film (xα′) formed in the step (1A) simultaneously.

[17] A method for producing a pressure sensitive adhesive sheetaccording to the above [14], which includes at least the following steps(1B) and (2B):

step (1B): a step of forming, on a layer (Xβ) mainly containing a resinpart (X) that is provided on a substrate or a release material, acoating film (y′) formed by the composition (y) containing the fineparticles in an amount of 15% by mass or more and a coating film (xα′)formed by the composition (xα) containing a resin as a main component,by laminating in this order.

[18] A viscoelastic layer formed of a multilayer structure of 3 or morelayers including a fine particle-containing layer that contains fineparticles, wherein:

the fine particle-containing layer is formed not as the outermost layerof the viscoelastic layer, and

one or more concave portions are formed on at least one surface of theviscoelastic layer, and the shapes of the one or more concave portionshave irregular shapes.

Advantageous Effects of Invention

The pressure sensitive adhesive sheet of the present invention hasexcellent air escape property capable of readily removing airaccumulation that may be formed on attaching to an adherend, and hasgood blister resistance and pressure sensitive adhesion characteristics.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross sectional view showing an example of thestructure of the pressure sensitive adhesive sheet of the presentinvention.

FIG. 2 is a schematic cross sectional view showing an example of theshape of the resin layer on the side of the surface (α) of the pressuresensitive adhesive sheet of the present invention.

FIG. 3 is a schematic plan view showing an example of the surface (α) ofthe resin layer of the pressure sensitive adhesive sheet of the presentinvention.

FIG. 4 is images of the pressure sensitive adhesive sheet produced inExample 1, taken through a scanning electron microscope; and (a) of FIG.4 is an image of a cross section of the pressure sensitive adhesivesheet, and (b) of FIG. 4 is a perspective image in observation of theside of the surface (α) of the resin layer of the pressure sensitiveadhesive sheet.

FIG. 5 is images obtained by observing the pressure sensitive adhesivesheet produced in Example 10 with a scanning electron microscope, inwhich (a) of FIG. 5 is an image of a cross section of the pressuresensitive adhesive sheet, and (b) of FIG. 5 is a perspective image inobservation on the side of the surface (α) of the resin layer of thepressure sensitive adhesive sheet.

FIG. 6 is images obtained by observing the pressure sensitive adhesivesheet produced in Comparative Example 1 with a scanning electronmicroscope, in which (a) of FIG. 6 is a cross sectional image of thepressure sensitive adhesive sheet, and (b) of FIG. 6 is a perspectiveimage in observation on the side of the surface (α) of the resin layerof the pressure sensitive adhesive sheet.

DESCRIPTION OF EMBODIMENTS

In the present invention, for example, an expression “YY containing acomponent XX as a main component” or an expression “YY mainly containinga component XX” means that “among the components contained in YY, acomponent having a largest content is the component XX”. A concretecontent of the component XX in this expression is generally 50% by massor more, and is preferably 65 to 100% by mass, more preferably 75 to100% by mass, even more preferably 85 to 100% by mass, relative to thetotal amount (100% by mass) of YY.

In the present invention, for example, “(meth)acrylic acid” indicatesboth “acrylic acid” and “methacrylic acid”, and the same shall apply toother similarity terms.

Regarding a preferred numerical range (for example, a range of contentor the like), a lower limit and an upper limit that are expressed instages can be combined each independently. For example, from anexpression of “preferably 10 to 90, more preferably 30 to 60”, “thepreferred lower limit (10)” and “the preferred upper limit (60)” may becombined to be “10 to 60”.

[Configuration of Pressure Sensitive Adhesive Sheet]

First, the configuration of the pressure sensitive adhesive sheet of thepresent invention is described.

The pressure sensitive adhesive sheet of the present invention has aresin layer, on a substrate or a release material, in which the resinlayer is formed of a multilayer structure of 3 or more layers includinga fine particle-containing layer that contains fine particles.

FIG. 1 includes schematic cross-sectional views of pressure sensitiveadhesive sheets, showing examples of a configuration of the pressuresensitive adhesive sheet of the present invention. This shows examplesof a configuration of the pressure sensitive adhesive sheet, in whichthe resin layer is formed of a multilayer structure of 3 or more layerscontaining a fine particle-containing layer.

As specific configurations of one embodiment of the pressure sensitiveadhesive sheet of the present invention, there are mentioned a pressuresensitive adhesive sheet 1 a having a resin layer 12 on a substrate 11as shown by FIG. 1(a); and a pressure sensitive adhesive sheet 1 bhaving a resin layer 12 on a release material 14 as shown by FIG. 1(b).

In the pressure sensitive adhesive sheet of the present invention, atleast a surface (α) 12 a of the resin layer 12 on the side opposite tothe side on which the substrate 11 or the release material 14 isprovided (hereinafter this may be simply referred to as “surface (α)”)has pressure sensitive adhesiveness.

Accordingly, from the viewpoint of handleability, the pressure sensitiveadhesive sheet of the embodiment of the present invention preferably hasa configuration of a pressure sensitive adhesive sheet 2 a or 2 b asshown by FIG. 1 (c) or FIG. 1 (d), where a release material 14 a isfurther arranged on the surface (α) 12 a of the resin layer 12 in thepressure sensitive adhesive sheet 1 a or 1 b shown in FIG. 1.

In the pressure sensitive adhesive sheet of the embodiment of thepresent invention, the surface (β) 12 b of the resin layer 12 on theside which the substrate 11 or the release material 14 is provided(hereinafter this may be simply referred to as “surface (β)”) may alsohave pressure sensitive adhesiveness. When the surface (β) also haspressure sensitive adhesiveness, in the pressure sensitive adhesivesheet 1 a or 2 a shown by FIG. 1 (a) or FIG. 1 (c), the adhesion betweenthe resin layer 12 and the substrate 11 can be good, and the pressuresensitive adhesive sheet 1 b or 2 b shown by FIG. 1 (b) or FIG. 1 (d)may be a double-sided pressure sensitive adhesive sheet.

Preferably, the resin layer 12 is formed of a multilayer structure of 3or more layers. For example, the pressure sensitive adhesive sheets 1 a,1 b, 2 a and 2 b in FIG. 1 have a resin layer 12 formed of a multilayerstructure of, as laminated in this order on a substrate or a releasematerial, a layer (Xβ) mainly containing a resin part (X), a fineparticle-containing layer (Y1) containing fine particles (hereinafterthis may be simply referred to as “layer (Y1)”), and a layer (Xα) mainlycontaining a resin part (X).

The fine particle-containing layer (Y1) is formed not as the outermostlayer of the resin layer 12. Namely, the surface (α) and the surface (β)are contained in a layer except the fine particle-containing layer (Y1).When the fine particle-containing layer (Y1) is formed as the outermostlayer of the resin layer 12, not only a sufficient pressure sensitiveadhesion characteristics could not be realized but also the appearanceof the pressure sensitive adhesive sheet is poor.

The above layer (Xα), the above layer (Y1) and the above layer (Xβ) eachmay be a single layer formed of one composition, but may also be amultilayer formed of two or more kinds of composition.

The configuration of the above-mentioned multilayer structure may besuch that, in the cross section in the thickness direction of the resinlayer, the boundary between the fine particle-containing layer (Y1) andthe other layer (layer (Xα) or layer (Xβ)) may be parallel to thehorizontal plane of the substrate or the release material like in thepressure sensitive adhesive sheet of FIG. 1, or may not be parallel butmay form a curved line or a polygonal line, but from the viewpoint ofeasy formation of one or more concave portions, the boundary ispreferably not parallel thereto.

Like in the pressure sensitive sheets 1 a to 2 b in FIG. 1, it ispreferable that the fine particle-containing layer (Y1) includes, asexisting therein intermittently relative to the horizontal planedirection of the substrate or the release material, a part denselycontaining fine particles and a part not containing fine particles.

The layer (Xβ) and the layer (Xα) each are a layer mainly containing theresin part (X), but may also contain the particle part (Y). However, thecontent of the particle part (Y) in the layer (Xβ) and the layer (Xα) iseach independently less than 15% by mass relative to the total mass(100% by mass) of the layer (Xβ) and the layer (Xα), and is smaller thanthe content of the resin that constitutes the resin part (X).

The layer (Xβ) and the layer (Xα) each may have a void part (Z) to bementioned below, in addition to the resin part (X) and the particle part(Y).

The content of the resin in the layer (Xβ) and the layer (Xα) is eachindependently generally 50 to 100% by mass, and is preferably 65 to 100%by mass, more preferably 75 to 100% by mass, even more preferably 85 to100% by mass, still more preferably 90 to 100% by mass, relative to thetotal mass (100% by mass) of the layer (Xβ) or the layer (Xα).

In the present invention, the “content of the resin in the layer (Xβ)and the layer (Xα)” may be considered to be the content of the resin inthe total amount (100% by mass (but excluding diluent solvent)) of theresin composition that is the forming material for the layer (Xβ) or thelayer (Xα).

The content of the fine particles constituting the particle part (Y) inthe layer (Xβ) and the layer (Xα) is each independently less than 15% bymass relative to the total mass (100% by mass) of the layer (Xβ) or thelayer (Xα), but is preferably 0 to 13% by mass, more preferably 0 to 10%by mass, even more preferably 0 to 5% by mass, still more preferably 0%by mass, relative to the total mass (100% by mass) of the layer (Xβ) orthe layer (Xα).

In the present invention, the “content of the fine particles in thelayer (Xβ) and the layer (Xα)” may be considered to be the content ofthe fine particles in the total amount (100% by mass (but excludingdiluent solvent)) of the resin composition that is the forming materialfor the layer (Xβ) or the layer (Xα).

Preferably, the layer (Xβ) and the layer (Xα) each are a layer formed ofa composition (xβ) or (xα) containing a resin as a main component to bementioned hereinunder, more preferably a layer formed of a composition(xβ) or (xα) containing a resin as a main component and having a contentof fine particles of less than 15% by mass.

The layer (Y1) containing the particle part (Y) in an amount of 15% bymass or more may be a layer formed of the particle part (Y) alone or mayalso be a layer containing the resin part (X) along with the particlepart (Y), and may further has a void part (Z) to be mentionedhereinunder.

The content of the fine particles constituting the particle part (Y) inthe layer (Y1) is 15% by mass or more, but is preferably 20 to 100% bymass, more preferably 25 to 90% by mass, even more preferably 30 to 85%by mass, still more preferably 35 to 80% by mass, relative to the totalmass (100% by mass) of the layer (Y1).

In the present invention, the “content of the fine particles in thelayer (Y1)” may also be considered to be the content of the fineparticles in the total amount (100% by mass (but excluding diluentsolvent)) of the composition that is the forming material for the layer(Y1).

The content of the resin in the layer (Y1) is generally 1 to 85% bymass, and is preferably 5 to 80% by mass, more preferably 10 to 75% bymass, even more preferably 20 to 70% by mass, still more preferably 25to 65% by mass, relative to the total mass (100% by mass) of the layer(Y1).

In the present invention, the “content of the resin in the layer (Y1)”may also be considered to be the content of the resin in the totalamount (100% by mass (but excluding diluent solvent)) of the compositionthat is the forming material for the layer (Y1).

Preferably, the layer (Y1) is a layer formed of a composition (y)containing fine particles to be mentioned hereinunder, more preferably alayer formed of a composition (y) containing fine particles in an amountof 15 to 100% by mass.

One or more concave portions 13 exist on the surface (α) 12 a of theresin layer 12 that the pressure sensitive adhesive sheet of the presentinvention has.

Regarding the distribution pattern of the resin part (X) and theparticle part (Y) in the resin layer 12, the resin parts (X) and theparticle parts (Y) may be distributed almost evenly as one pattern, oras a different pattern, an area mainly containing the resin parts (X)and an area mainly containing the particle parts (Y) may be locallydivided.

In addition, as shown by FIG. 1 (a) to FIG. 1 (d), in the area where theone or more concave portions 13 exist on the surface (α) of the resinlayer 12, the pattern may be such that the proportion of the particleparts (Y) is smaller than in the other areas, or the particle parts (Y)may not be partly present.

On the surface (α) of the resin layer that the pressure sensitiveadhesive sheet of the present invention has, one or more concaveportions exist and the shapes of the one or more concave portions haveirregular shapes.

In a planar view of the one or more concave portions 13 existing on thesurface (α), the length of the concave portion 13 is not specificallylimited. Namely, the concave portions 13 may include relatively longgroove-like ones or relatively short pit-like ones.

The concave portions 13 existing on the surface (α) play a role ofair-discharge channels for removing outside the “air accumulation” to beformed in adhering the pressure sensitive adhesive sheet of the presentinvention to an adherend.

Here, the wording “the shapes of the one or more concave portions haveirregular shapes” mean that in a planar view or a stereoscopic viewthereof, the shapes of the one or more concave portions do not have anyspecific shapes such as a shape surrounded by a circle or a line alone(triangle, square, etc.) but have irregular shapes with neitherregularities nor similarities between the shapes of the individualconcave portions.

For judgement whether or not “the shapes of the concave portions on thesurface (α) have irregular shapes”, in principle, the shapes of the oneor more concave portion on the surface (α) are observed visually or witha digital microscope (magnification: 30 to 100). In the case where theplane shapes of one or more concave portions in a planar view from theside of the surface (α) are judged to have irregular shapes, it may beconsidered that the “shapes of the one or more concave portions haveirregular shapes”.

However, in the case where 10 regions (R) each surrounded by anarbitrarily selected having an edge strength of 4 mm on the surface (α)are selected and where the shapes of the one or more concave portionsexisting in each region (R) are observed visually or with a digitalmicroscope (magnification: 30 to 100) in a planar view (if desired, in astereoscopic view) from the side of the surface (α), when the shapes ofthe one or more concave portions existing in all of the selected 10regions are judged to have irregular shapes, it may be considered thatthe “shapes of the one or more concave portions on the surface (α) ofthe resin layer have irregular shapes”.

In the case where the region (R) is larger than a photographable regionwith a digital microscope, plural images taken in the neighboringphotographable regions are combined to be one image of the region (R),which may be used for the above judgement.

In this description as the digital microscope for observation of variousshapes, for example, “Digital Microscope VHX-1000” or “DigitalMicroscope VHX-5000”, both trade names manufactured by KeyenceCorporation may be used.

Like the pressure sensitive adhesive sheet described in PTL 1, apressure sensitive adhesive sheet having a pressure sensitive adhesivelayer with pre-designed determinate grooves formed on the surfacethereof through embossed pattern transfer is known. In the pressuresensitive adhesive sheet of the type, the shapes of the grooves aredeterminate, and even though the shapes of the grooves are so planned asto improve at least one characteristic selected from air escapeproperty, appearance, pressure sensitive adhesion characteristics andpunching property, the other characteristics often worsen in many cases.

The present inventors have specifically noted that, for example, theshape of the grooves capable of contributing toward improving air escapeproperty and the shape of the grooves capable of improving pressuresensitive adhesion characteristics differ from each other in point ofthe shape of the grooves that are required to improve the individualcharacteristics, and have found out the technical meaning of thepresence of irregular concave portions on the surface (α) of the resinlayer having pressure sensitive adhesiveness.

Namely, in the pressure sensitive adhesive sheet of the presentinvention, the one or more concave portions existing on the surface (α)of the resin layer have irregular shapes, and such concave portionsdiffering from each other in point of the degree of contribution towardvarious characteristics of air escape property, appearance, pressuresensitive adhesion characteristics and punching property are formed onthat surface, and consequently, these characteristics of the pressuresensitive adhesive sheet can be thereby well-balanced.

From the viewpoint of providing a pressure sensitive adhesive sheethaving improved air escape property, it is preferable that the irregularshapes of the one or more concave portion can be visually recognizedfrom the side of the exposed surface (α) of the resin layer by observingwith naked eyes. In the pressure sensitive adhesive sheet 2 a or 2 bwhere the release material 14 a is further provided on the surface (α)12 a of the resin layer 12, as shown in FIG. 1 (c) or FIG. 1 (d), it ispreferable that, when the release material 14 a is peeled away, suchirregular shapes of the one or more concave portions can be visuallyrecognized from the side of the exposed surface (α) by observing withnaked eyes.

Preferably, the one or more concave portions are formed throughself-formation of the resin layer.

In the present invention, “self-formation” means a phenomenon ofnaturally forming a disorganized profile in a process of self-sustainingformation of a resin layer, and more precisely, means a phenomenon ofnaturally forming a disorganized profile in a process of self-sustainingformation of a resin layer by drying a coating film formed of acomposition that is a forming material for a resin layer.

The shapes of the one or more concave portions thus formed throughself-formation of the resin layer in the manner as above may becontrolled in some degree by controlling the drying condition or thekind and the content of the component in the composition that is aforming material for the resin layer, but differ from grooves to beformed through embossed pattern transfer, and it may be said that “it issubstantially impossible to reproduce exactly the same shapes”.Consequently, it may be said that the one or more concave portionsformed through self-formation of the resin layer could have irregularshapes.

The forming process of the one or more concave portions formed throughself-formation of the resin layer is considered to be as follows.

First, during formation of a coating film of a composition that containsfine particles as a forming material for the particle part (Y), fineparticles exist at random in the coating film.

Here, in the step of drying the coating film, contraction stressdevelops inside the coating film, and in the part where the bondingforce of the resin would have attenuated owing to the presence of thefine particles therein, the coating film is cracked inside it. Withthat, it is considered that the resin around the cracked part may flowinto the space temporarily formed by cracking to thereby form one ormore concave portions on the surface (α) of the resin layer.

In addition, it is considered that, in the drying step for the coatingfilm, when cracks are formed inside the coating film, the fine particlesoriginally having existed therein would be pushed away into other parts,and therefore the proportion of the particle part (Y) in the sites wherethe one or more concave portions are formed would be smaller than in theother sites.

The one or more concave portions are easy to form, for example, byseparately forming a coating film of a composition having a high contentof fine particles and having a low content of resin, and a coating filmof a composition containing a resin as a main component, and drying thetwo coating films simultaneously.

It is considered that, when two coating films that differ in the resincontent are formed and then the two coating films are driedsimultaneously, a contraction stress difference could be generatedinside the coating films being dried, and the coating films could bethereby readily cracked.

From the viewpoint of readily forming the one or more concave portions,it is recommended to control the condition appropriately inconsideration of the following matters. It is considered that thesematters could react with each other in a complex form to facilitate theformation of the one or more concave portions. In this connection,preferred embodiments of the matters for facilitating the formation ofthe one or more concave portions are as described in the correspondingsections to be given hereinunder.

-   -   The kind, constituent monomers, molecular weight and content of        the resin contained in the composition of the forming material        for the coating film.    -   The kind of the crosslinking agent and the kind of the solvent        contained in the composition of the forming material for the        coating film.    -   The viscosity and the solid concentration of the composition of        the forming material for the coating film.    -   The shape, kind and mass concentration of fine particles.    -   The dispersion state of the fine particles in the composition of        the forming material for the coating film and in the coating        film, and the content of the fine particles.    -   The thickness of the coating film to be formed.    -   The drying temperature and the drying time for the formed        coating film.

In formation of the pressure sensitive adhesive layer in an ordinarypressure sensitive adhesive sheet, it is intended to form the pressuresensitive adhesive layer having a flat surface, and the above-mentionedmatters are suitably settled in many cases.

On the other hand, in the present invention, the above matters are sosettled that the one or more concave portions capable of contributingtoward improvement of the air escape property of the pressure sensitiveadhesive sheet can be formed, quite differing from those in the planningmethod for the pressure sensitive adhesive layer of ordinary pressuresensitive adhesive sheets.

Preferably, the above-mentioned matters are suitably settled inconsideration of the flowability of the fine particles and the resincontained in the coating film to be formed.

For example, by controlling the viscosity of the coating film formed ofa composition containing a large amount of fine particles to fall withina suitable range, it is possible to suitably prevent the formed coatingfilm from being mixed with any other coating film (a coating filmcontaining a large amount of resin) while the predetermined flowabilityof the fine particles in the coating film could be maintained as such.By such controlling, cracks could be readily formed in the horizontaldirection to facilitate formation of one or more concave portions in thecoating film containing a large amount of resin.

As a result, it may be possible to increase the proportion of the one ormore concave portions to be formed on the surface (α) and to increasethe proportion of the one or more concave portions connecting to eachother, thereby giving a pressure sensitive adhesive sheet having a moresuperior air escape property.

Among the above-mentioned matters, it is desirable to suitably controlthe kind, the constituent monomers and the molecular weight of the resinand the resin content so that the resin contained in the coating filmcontaining a large amount of resin could have a suitableviscoelasticity.

Namely, by suitably increasing the hardness of the coating film (thehardness thereof that may be determined various factors such as theviscoelasticity of resin, the viscosity of the coating liquid, etc.),the contract stress of the resin part (X) increases to facilitate theformation of one or more concave portions. When the hardness of thecoating film is higher, the contraction stress could be higher tofacilitate the formation of one or more concave portions, but when thecoating film is too hard, the coatability thereof may worsen. Inaddition, when the resin elasticity is increased too much, the adhesivestrength of the resin layer to be formed from the coating film tends tolower. In consideration of these, it is desirable to suitably controlthe viscoelasticity of the resin.

It is considered that, by suitably selecting the fine particles and theresin to thereby make the dispersion condition of the fine particlesappropriate, the degree of swelling of the thickness of the resin layerowing to the fine particles therein and the self-forming power of theone or more concave portions could be thereby controlled and, as aresult, the one or more concave portions could be readily formed on thesurface (α).

Further, in consideration of the crosslinking speed of the formedcoating film (or the composition of the forming material), it isdesirable that the above-mentioned matters are suitably settled.

Namely, in the case where the crosslinking speed of the coating film istoo high, the coating film would be cured before formation of one ormore concave portions therein. In addition, in the case, there may besome influences on the degree of cracking of the coating film.

The crosslinking speed of the coating film may be controlled by suitablydefining the kind of the crosslinking agent and the kind of the solventin the composition of the forming material or by suitably settling thedrying time and the drying temperature for the coating film.

It is desirable that the one or more concave portions on the surface (α)of the resin layer that the pressure sensitive adhesive sheet of thepresent invention has do not have a predetermined pattern. Here,“predetermined pattern” means, when a shape of one concave portion isnoted, the shape to be a certain repeating unit that the concave portionhas.

The one or more concave portions on the surface (α) of the resin layerare, from the viewpoint of providing a pressure sensitive adhesive sheethaving well-balanced characteristics of air escape property, appearance,pressure sensitive adhesion characteristics and punching property,preferably not those formed, for example, through embossed patterntransfer of pressing an embossed pattern-having release material againstthe surface of the resin layer.

Preferably, the pressure sensitive adhesive sheet of the presentinvention has, as shown by FIG. 1 (a) to FIG. 1 (d), plural concaveportions 13 on the surface (α) of the resin layer 12 being opposite tothe side on which the substrate 11 or the release material 14 isprovided.

Also preferably, the concave portions 13 on the surface (α) of thepressure sensitive adhesive sheet of the present invention are thosesatisfying at least one or more of the following requirements (I) to(IV), more preferably, the concave portions satisfying the requirement(I) further satisfy any one or more of the requirements (II) to (IV),and even more preferably the concave portions satisfying the requirement(I) satisfy all the requirements (II), (III) and (IV).

Requirement (I): The plural concave portions have a maximum heightdifference of 0.5 μm or more.

Requirement (II): Plural concave portions exist on the surface (α) ofthe resin layer, and 95% or more of the plural concave portions haveshapes each differing from each other.

Requirement (III): One or more of the above concave portions exists in aregion (Q) surrounded by an arbitrarily selected square having an edgestrength of 1 mm on the surface (α).

Requirement (IV): Plural concave portions exist on the surface (α) ofthe resin layer, and the positions of the plural concave portions haveno periodicity.

The requirements (I) to (IV) are described in detail hereinunder.

<Requirement (I)>

FIG. 2 includes schematic cross-sectional views of a resin layer,showing examples of a shape on the side of the surface (α) of the resinlayer that the pressure sensitive adhesive sheet of the presentinvention has.

Like the concave portion 13 shown in FIG. 2(a), the shape of an ordinaryconcave portion has two mountain parts (M₁) and (M₂) and a valley part(N). The “height difference” of the concave portion in the presentinvention means the length of the difference (h) between the highestposition (m) of the two mountain parts (M₁) and (M₂) (in FIG. 2(a), themaximum point of the mountain part (M₁)) and the lowest position (n)thereof (in FIG. 2(a), the minimum point of the valley part (N)),relative to the thickness direction of the resin layer 12.

It is considered that the case of FIG. 2(b) would have two concaveportions of a concave portion 131 having two mountain parts (M₁₁) and(M₁₂) and a valley part (N₁), and a concave portion 132 having twomountain parts (M₁₂) and (M₁₃) and a valley part (N₂). In this case, thelength of the difference (h₁) between the maximum point of the mountainpart (M₁₁) and the minimum point of the valley part (N₁) indicates theheight difference of the concave portion 131, and the length of thedifference (h₂) between the maximum point of the mountain part (M₁₃) andthe minimum point of the valley part (N₂) indicates the heightdifference of the concave portion 132.

“One or more concave portions” defined by the requirement (I) indicatesconcave portions having a maximum height difference of 0.5 μm or more.The “concave portions” defined by the requirement (I) may be any oneshaving a height difference of 0.5 μm or more in any site thereof, andare not required to have the height difference throughout the entireregion of the concave portions.

Preferably, plural concave portions satisfying the requirement (I)exist.

Regarding the presence or absence of plural concave portions satisfyingthe requirement (I), a region (P) surrounded by an arbitrarily selectedsquare having an edge strength of 5 mm on the surface (α) of the resinlayer of the pressure sensitive adhesive sheet is observed with anelectronic microscope for the judgment. More specifically, the presenceor absence is judged according to the method described in the section ofExamples.

The maximum value of the height difference of one concave portion is,from the viewpoint of improving the air escape property of the pressuresensitive adhesive sheet, from the viewpoint of keeping the appearanceof the pressure sensitive adhesive sheet good, and from the viewpoint ofthe shape stability of the pressure sensitive adhesive sheet, morepreferably 1.0 μm or more and not more than the thickness of the resinlayer, further preferably 3.0 μm or more and not more than the thicknessof the resin layer, and still further preferably 5.0 μm or more and notmore than the thickness of the resin layer.

The ratio of the maximum height difference of plural concave portionsexisting inside the region (P) to the thickness of the resin layer[maximum height difference/thickness of resin layer] is preferably 1/100to 100/100, more preferably 5/100 to 99/100, even more preferably 10/100to 96/100, still more preferably 15/100 to 90/100.

The mean value of the width of the concave portions is, from theviewpoint of improving the air escape property of the pressure sensitiveadhesive sheet and from the viewpoint of bettering the pressuresensitive adhesiveness of the pressure sensitive adhesive sheet,preferably 1 to 500 more preferably 3 to 400 μm, even more preferably 5to 300 μm.

In the present invention, the width of the concave portion means thedistance between the maximum points of the two mountain parts, and inthe concave portion 13 shown in FIG. 2(a), the width indicates thedistance L between the mountain part (M₁) and the mountain part (M₂). Inthe concave portion 131 shown in FIG. 2(b), the width indicates thedistance L₁ between the mountain part (M₁₁) and the mountain part (M₁₂),and in the concave portion 132 therein, the width indicates the distanceL₂ between the mountain part (M₁₃) and the mountain part (M₁₂).

In a planar view of the pressure sensitive adhesive sheet of the presentinvention (when the sheet is viewed from directly above), when theconcave portion has a long wide and a short side, the short side is thewidth.

The ratio of the maximum height difference of one concave portion to themean value of the width [maximum height difference/mean value of width)(in the concave portion 13 shown in FIG. 2(a), the ratio is “h/L”) is,from the viewpoint of improving the air escape property of the pressuresensitive adhesive sheet and from the viewpoint of bettering thepressure sensitive adhesiveness of the pressure sensitive adhesivesheet, preferably 1/500 to 100/1, more preferably 3/400 to 70/3, evenmore preferably 1/60 to 10/1.

<Requirement (II)>

Like the above-mentioned requirement (II), it is preferable that, in thepressure sensitive adhesive sheet of the present invention, pluralconcave portions exist on the surface (α), and 95% or more of the pluralconcave portions have shapes differing from each other.

Presence of the plural concave portions satisfying the requirement (II)on the surface (α) of the resin layer makes it possible to provide apressure sensitive adhesive sheet having well-balanced characteristicsof air escape property, appearance, pressure sensitive adhesioncharacteristics and punching property.

In one embodiment of the pressure sensitive adhesive sheet of thepresent invention, the proportion of the plural concave portionsexisting on the surface (α) of the resin layer and having shapesdiffering from each other is more preferably 98% or more relative to thetotal number (100%) of the concave portions existing on the surface (α),even more preferably 100%.

In the present invention, for judgement whether or not the concaveportions satisfy the requirement (II), the shapes of plural concaveportions existing in a region (P) surrounded by an arbitrarily selectedsquare having an edge strength of 5 mm on the surface (α) of the resinlayer of the targeted pressure sensitive adhesive sheet are observedwith an electron microscope (magnification: 30 to 100), and when thenumber of the concave portions having shapes differing from each otheris preferably 95% or more (more preferably 98% or more, even morepreferably 100%) relative to the total number of the plural concaveportions observed in the region (P), the pressure sensitive adhesivesheet is judged to satisfy the requirement (II). For observation of theshapes of the plural concave portions, a method of directly observingthe sheet with an electronic microscope having the above-mentionedmagnification may be employed, or a method of taking a picture of thesheet using an electronic microscope having the above-mentionedmagnification, and visually observing the shapes of the plural concaveportions shown on the image may also be employed. More specifically, thesatisfaction of the requirement may be judged according to the methoddescribed in the section of Examples.

Here, “the number of the concave portions having shapes differing fromeach other is 100%” means that “all the plural concave portions observedinside the region (P) have shapes differing from each other”.

In this description, the concave portions connected uninterruptedly toeach other in a selected region (P) are counted as “one concaveportion”. However, when two concave portions existing in a selectedregion bond to one concave portion in the other region adjacent to thatselected region to form one concave portion, the two concave portions inthe selected region should be counted as independent ones.

<Requirement (III)>

FIG. 3 (a) and FIG. 3 (b) each are a schematic plan view of the surface(α), showing one example of the surface (α) of the resin layer that thepressure sensitive adhesive sheet of the present invention has. As shownin FIG. 3(a), plural concave portions 13 and 130 exist on the surface(α) 12 a of the resin layer 12 of the pressure sensitive adhesive sheetof the present invention.

Here, the pressure sensitive adhesive sheet of the present inventionhas, as in the above-mentioned requirement (III), one or more concaveportions 13 and 130 in the region (Q) surrounded by an arbitrarilyselected square 50 square having an edge strength of 1 mm (hereinafter,1-mm square 50) on the surface (α) 12 a. In FIG. 3(a), eight concaveportions exist in the region (Q).

In that manner, presence of one or more concave portions in the region(Q) on the surface (α) improves the air escape property of the pressuresensitive adhesive sheet.

In the present invention, the number of the concave portions existing inthe region (Q) on the surface (α) is preferably one or more, but is,from the above-mentioned viewpoint, more preferably 2 or more, even morepreferably 3 or more, and on the other hand, from the viewpoint ofbettering the appearance and the pressure sensitive adhesioncharacteristics, the number is preferably 1000 or less, more preferably500 or less.

From the viewpoint of improving the air escape property of the pressuresensitive adhesive sheet, it is preferable that one or more of theabove-mentioned concave portions 13 and 130 existing in the region (Q onthe surface (α) 12 a of the resin layer 12 that one embodiment of thepressure sensitive adhesive sheet of the present invention has extendtoward any side of the 1-mm square 50 that is a boundary line of theregion (Q), as in FIG. 3(a)

On the surface (α) 12 a of the resin layer 12 of the pressure sensitiveadhesive sheet shown by FIG. 3(a), the number of the cross lines 13 abetween the extending concave portion 13 or 130 and any side of the 1-mmsquare 50 that is a boundary line of the region (Q) is 9 as a whole.

The number of the cross lines between the concave portion and any sideof the square having an edge length of 1 mm, which is a boundary line ofthe region (Q), is preferably 1 or more, more preferably 2 or more, evenmore preferably 3 or more.

From the viewpoint of providing a pressure sensitive adhesive sheethaving more improved air escape property, one or more concave portionsexisting in the region (Q) on the surface (α) of the resin layer thatone embodiment of the pressure sensitive adhesive sheet of the presentinvention has preferably have a shape that continuously extends into theother one or more regions (Q′) surrounded by a square having an edgelength of 1 mm, which is adjacent to the region (Q), more preferablyhave a shape that continuously extends into the other two or moreregions (Q′), and even more preferably have a shape that continuouslyextends into the other three or more regions (Q′),

For example, in FIG. 3(b), the region (Q) surrounded by a 1-mm square 50arbitrarily selected on the surface (α) 12 a of the resin layer 12 isspecifically noted. The “other region (Q′) surrounded by a square havingan edge length of 1 mm, which is adjacent to the region (Q)” indicatesthe region (Q′1) surrounded by the square 501 having an edge length of 1mm (hereinafter, 1-mm square 501), the region (Q′2) surrounded by thesquare 502 having an edge length of 1 mm (hereinafter, 1-mm square 502),the region (Q′3) surrounded by the square 503 having an edge length of 1mm (hereinafter, 1-mm square 503), and the region (Q′4) surrounded bythe square 504 having an edge length of 1 mm (hereinafter, 1-mm square504).

Further, the “concave portion 130” existing on the surface (α) 12 a ofthe resin layer 12 shown in FIG. 3(b) is specifically noted. The“concave portion 130” is a region existing in the region (Q) surroundedby the 1-mm square 50, and has a shape extending into the region (Q′1)surrounded by the 1-mm square 501 adjacent to the region (Q), into theregion (Q′2) surrounded by the 1-mm square 502, and into the region(Q′4) surrounded by the 1-mm square 504.

Presence of the concave portion having a shape extending not only intothe region (Q) but also into the other region (Q′) adjacent to theregion (Q) on the surface (α), like the “concave portion 130” shown inFIG. 3(b), provides a pressure sensitive adhesive sheet having moreimproved air escape property.

In addition, it is preferable that the concave portions existing in theregion (Q) on the surface (α) of the resin layer have a shape extendingnot only into one or more other region (Q′) adjacent to the region (Q)but also further continuously into any other regions (Q″) than theregion (Q), which are adjacent to the other region (Q′).

For example, the “concave portion 130” shown in FIG. 3(b) has a shapeextending not only into the region (Q′4) adjacent to the region (Q) butalso further continuously into the region (Q′5) adjacent to the region(Q′4).

<Requirement (IV)>

In one embodiment of the pressure sensitive adhesive sheet of thepresent invention, preferably, the positions of the plural concaveportions existing on the surface (α) of the resin layer of the pressuresensitive adhesive sheet have no periodicity from the viewpoint ofproviding a pressure sensitive adhesive sheet having well-balancedcharacteristics of air escape property, appearance, pressure sensitiveadhesion characteristics and punching property.

In the present invention, the wording “the positions of the pluralconcave portions have no periodicity” means a state where the pluralconcave portions exist at random not having the same repeating pattern.Namely, the state differs from a state of “arrangement” based onspecific regularity, like that for the grooves described in PTL 1, thatis, like that for grooves formed through embossed pattern transfer ofpressing a release material having an embossed pattern to the surface ofa resin layer.

For judgement whether or not “the positions of plural concave portionshave no periodicity”, in principle, the positions of the plural concaveportions existing on the surface (α) of the resin layer of the targetedpressure sensitive adhesive sheet are identified through visualobservation thereof or through observation thereof with a digitalmicroscope (magnification: 30 to 100).

However, for the judgement, ten regions (R) each surrounded by anarbitrarily selected square having an edge length of 4 mm on the surface(α) are selected, and the “positions of the plural concave portions”existing inside the region (R) may be identified visually or with adigital microscope (magnification: 30 to 100). Namely, when the“positions of plural concave portions” existing in all the selected tenregions do not have any periodicity, the targeted pressure sensitiveadhesive sheet can be considered to satisfy the requirement (IV).

For the observation, a method of direct observation thereof with anelectron microscope at the magnification as mentioned above may beemployed, or a method of taking an image thereof with a digitalmicroscope having the above-mentioned magnification, followed byvisually observing the positions of the plural concave portions shown inthe image may also be employed.

From the viewpoint of providing a pressure sensitive adhesive sheethaving well-balanced characteristics of air escape property, appearance,pressure sensitive adhesion characteristics and punching property, it ispreferable that the shape of an attached face on the surface (α) of theresin layer of one embodiment of the pressure sensitive adhesive sheetof the present invention has an irregular shape.

In the present invention, “attached face on the surface (α)” means asurface from which the range occupied by the plural concave portions onthe surface (α) of the resin layer is excluded, and means a face that isto be attached to an adherend when an adherend is attached to thepressure sensitive adhesive sheet. FIG. 3(a) shows a schematic plan viewof the surface (α), showing one example of the surface (α) of the resinlayer that one embodiment of the pressure sensitive adhesive sheet ofthe present invention has, and the “attached face” indicates the shadedpart except the plural concave portions 13 of the surface (α) 12 a ofthe resin layer shown in FIG. 3.

“Irregular shape” means that the shape does not have any specific shapesuch as a shape surrounded by a circle or a line alone (triangle,square, etc.) and the shape therefore does not have any regularity as ashape of the shaded part of the surface (α) 12 a of the resin layershown in FIG. 3(a), and an attached face to be formed through embossedpattern transfer of pressing an embossed pattern-having release materialagainst the surface of a resin layer or the like is excluded.

In other words, in the pressure sensitive adhesive sheet satisfying therequirement (II), it is considered that the shape of the attached faceon the surface (α) would have an irregular shape.

For judgement whether or not “the shape of the attached face on thesurface (α) has an irregular shape”, in principle, the shape of theattached face on the surface (α) of the resin layer of the targetedpressure sensitive adhesive sheet is observed visually or with a digitalmicroscope (magnification: 30 to 100).

However, for the judgement, ten regions (R) each surrounded by anarbitrarily selected square having an edge length of 4 mm on the surface(α) are selected, and the “shape of the attached face” in the region (R)may be observed visually or with a digital microscope (magnification: 30to 100). Namely, when the “shape of the attached face” in each of theselected ten regions is judged to have an irregular shape, it may beconsidered that in the targeted pressure sensitive adhesive sheet, the“shape of the attached face on the surface (α) has an irregular shape”

For the observation of the shape of the attached face, a method ofdirect observation thereof with an electron microscope at themagnification as mentioned above may be employed, or a method of takingan image thereof with a digital microscope having the above-mentionedmagnification, followed by visually observing the shape of the attachedface on the image may also be employed.

In the following, each constitution of the pressure sensitive adhesivesheet of the present invention will be described.

Substrate

The substrate used in one embodiment of the present invention is notparticularly limited, and examples thereof include a paper substrate, aresin film or sheet, and a substrate containing a paper substratelaminated with a resin, which may be appropriately selected depending onthe purpose of the pressure sensitive adhesive sheet according to oneembodiment of the present invention.

Examples of paper constituting the paper substrate include thin paper,medium quality paper, wood-free paper, impregnated paper, coated paper,art paper, parchment paper, and glassine paper.

Examples of the resin constituting the resin film or sheet include apolyolefin resin, such as polyethylene and polypropylene; a vinyl resin,such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol,an ethylene-vinyl acetate copolymer, and an ethylene-vinyl alcoholcopolymer; a polyester resin, such as polyethylene terephthalate,polybutylene terephthalate, and polyethylene naphthalate; polystyrene;an acrylonitrile-butadiene-styrene copolymer; cellulose triacetate;polycarbonate; a urethane resin, such as polyurethane andacrylic-modified polyurethane; polymethylpentene; polysulfone; polyetherether ketone; polyether sulfone; polyphenylenesulfide; a polyimideresin, such as polyether imide and polyimdie; a polyamide resin; anacrylic resin; and a fluorine resin.

Examples of the substrate containing a paper substrate laminated with aresin include laminated paper containing the aforementioned papersubstrate laminated with a thermoplastic resin, such as polyethylene.

Among these substrates, a resin film or sheet is preferred, a film orsheet formed of a polyester resin is more preferred, and a film or sheetformed of polyethylene terephthalate (PET) is further preferred.

In the case where the pressure sensitive adhesive sheet of the presentinvention is applied to a purpose that requires heat resistance, a filmor sheet constituted by a resin selected from polyethylene naphthalateand a polyimide resin is preferred, and in the case where the pressuresensitive adhesive sheet is applied to a purpose that requires weatherresistance, a film or sheet constituted by a resin selected frompolyvinyl chloride, polyvinylidene chloride, an acrylic resin, and afluorine resin is preferred.

The thickness of the substrate may be appropriately determined dependingon the purpose of the pressure sensitive adhesive sheet of the presentinvention, and is preferably from 5 to 1,000 μm, more preferably from 10to 500 μm, further preferably from 12 to 250 μm, and still furtherpreferably from 15 to 150 μm, from the standpoint of the handleabilityand the economic efficiency.

The substrate may further contain various additives, such as anultraviolet ray absorbent, a light stabilizer, an antioxidant, anantistatic agent, a slipping agent, an antiblocking agent, and acolorant.

The substrate used in one embodiment of the present invention ispreferably a non-air permeable substrate from the standpoint ofenhancing the blister resistance of the resulting pressure sensitiveadhesive sheet, and specifically a substrate containing theaforementioned resin film or sheet having a metal layer on the surfacethereof.

Examples of the metal forming the metal layer include a metal havingmetallic gloss, such as aluminum, tin, chromium, and titanium.

Examples of the method of forming the metal layer include a method ofvapor-depositing the metal by a PVD method, such as vacuum vapordeposition, sputtering, and ion plating, and a method of attaching ametal foil formed of the metal with an ordinary pressure sensitiveadhesive, and a method of vapor-depositing the metal by a PVD method ispreferred.

In the case where a resin film or sheet is used as the substrate, thesurface of the resin film or sheet may be subjected to a surfacetreatment by an oxidizing method, a roughening method, and the like, ormay be subjected to a primer treatment, from the standpoint of enhancingthe adhesion to the resin layer to be laminated on the resin film orsheet.

Examples of the oxidizing method include a corona discharge treatment, aplasma discharge treatment, a chromic acid treatment (wet process), ahot air treatment, and an ozone treatment, and an ultraviolet rayirradiation treatment, and examples of the roughening treatment includea sand blasting treatment and a solvent treatment.

Release Material

The release material used in one embodiment of the present invention maybe a release sheet having both surfaces subjected to a releasetreatment, and a release sheet having one surface subjected to a releasetreatment, and examples thereof include a substrate for the releasematerial having coated thereon a release agent. The release treatment ispreferably performed on a flat release material without a relief shapeformed thereon (for example, a release material having no emboss patternformed thereon).

Examples of the substrate for the release material include the papersubstrate, the resin film or sheet, and the substrate containing a papersubstrate laminated with a resin described above used as the substrateof the pressure sensitive adhesive sheet according to one embodiment ofthe present invention.

Examples of the release agent include a rubber elastomer, such as asilicone resin, an olefin resin, an isoprene resin, and a butadieneresin, a long-chain alkyl resin, an alkyd resin, and a fluorine resin.

The thickness of the release material is not particularly limited, andis preferably from 10 to 200 μm, more preferably from 25 to 170 μm, andfurther preferably from 35 to 80 μm.

[Resin Layer]

The resin layer that the pressure sensitive adhesive sheet of thepresent invention has is formed of a multilayer structure of 3 or morelayers including a fine particle-containing layer that contains fineparticles. The fine particle-containing layer is formed not as theoutermost layer of the resin layer.

Regarding the resin layer that the pressure sensitive adhesive sheet ofthe present invention has, the surface (α) of the resin layer on theside opposite to the side thereof on which at least a substrate or arelease material is provided has pressure sensitive adhesiveness, butthe surface (β) of the resin layer on the side on which the substrate orthe release material is provided may also has pressure sensitiveadhesiveness.

Preferably, the resin layer that one embodiment of the pressuresensitive adhesive sheet of the present invention additionally has avoid part (Z) in addition to the resin part (X) and the particle part(Y). The void part (Z), if any, in the resin layer can improve theblister resistance of the pressure sensitive adhesive sheet.

The void part (Z) includes the voids existing between the fine particlesand, when the fine particles are secondary particles, the voids existinginside the secondary particles.

In the case where the resin layer has a multilayer structure, eventhough a void part (Z) exists in the process of forming the resin layeror just after formation of the layer, the resin part (X) may flow intothe void part (Z) and therefore the voids may disappear to give a resinlayer not having the void part (Z).

However, even in the case where a void part (Z) having existed in theresin layer for a period of time has disappeared, the resin layer thatone embodiment of the pressure sensitive adhesive sheet of the presentinvention has may have one or more concave portions on the surface (α)and can be therefore excellent in air escape property and blisterresistance.

The shear storage elastic modulus at 100° C. of the resin layer that oneembodiment of the pressure sensitive adhesive sheet of the presentinvention has is, from the viewpoint of improving the air escapeproperty and the blister resistance of the pressure sensitive adhesivesheet, preferably 9.0×10³ Pa or more, more preferably 1.0×10⁴ Pa, evenmore preferably 2.0×10⁴ Pa or more.

In the present invention, the shear storage elastic modulus at 100° C.of the resin layer means a value measured with a viscoelastometer (forexample, apparatus name “DYNAMIC ANALYZER RDA II” manufactured byRheometrics Inc.) at a frequency of 1 Hz.

The thickness of the resin layer is preferably 1 to 300 μm, morepreferably 5 to 150 μm, even more preferably 10 to 75 μm.

The adhesive strength of the surface (α) of the resin layer of oneembodiment of the pressure sensitive adhesive sheet of the presentinvention is preferably 0.5 N/25 mm or more, more preferably 2.0 N/25 mmor more, even more preferably 3.0 N/25 mm or more, further morepreferably 4.0 N/25 mm or more, still further more preferably 7.0 N/25mm or more.

In the case where the surface (β) of the resin layer also has pressuresensitive adhesiveness, the adhesive strength of the surface (β)preferably belongs to the above-mentioned range.

The value of the adhesive strength of the pressure sensitive adhesivesheet means a value measured according to the method described in thesection of Examples.

<Resin Part (X)>

The resin part (X) constituting the resin layer contains a resin as amain component.

In the present invention, the resin part (X) is a part containing anyother component than fine particles contained in the resin layer, and inthis point, this is differentiated from the particle part (Y).

The resin part (X) contains a resin as a main component and may containa crosslinking agent and ordinary additives in addition to resin.

The content of the resin in the resin part (X) is generally 40% by massor more, and is preferably 50% by mass or more, more preferably 65% bymass or more, even more preferably 75% by mass or more, still morepreferably 85% by mass or more, further more preferably 90% by mass ormore, relative to the total amount (100% by mass) of the resin part (X),and is preferably 100% by mass or less, more preferably 99.9% by mass orless, relative to the total amount (100% by mass) of the resin part (X).

In the present invention, a value of the content of the resin in theresin composition to be the forming material for the resin part (X) maybe considered to be the above-mentioned “content of the resin in theresin part (X)”.

The resin to be contained in the resin part (X) is preferably a pressuresensitive adhesive resin from the viewpoint of making the surface (α) ofthe resin layer to be formed express pressure sensitive adhesiveness.

In particular, in the case where the resin layer has a multilayerstructure formed by laminating a layer (Xβ), a layer (Y1) and a layer(Xα) in this order from the side on which a substrate or a releasematerial is provided, like in the pressure sensitive adhesive sheets 1 ato 2 b of FIG. 1, it is desirable from the above-mentioned viewpointsthat at least the layer (Xα) contains a pressure sensitive adhesiveresin.

Examples of the pressure sensitive adhesive resin include acrylicresins, urethane resins, rubber resins, silicone resins, etc.

Among these pressure sensitive adhesive resins, an acrylic resin ispreferably contained from the viewpoint that the pressure sensitiveadhesion characteristics and the weather resistance thereof are good andthat the irregular concave portions are easy to form on the surface (α)of the resin layer to be formed.

The content of the acrylic resin is preferably 25 to 100% by mass, andis more preferably 50 to 100% by mass, even more preferably 70 to 100%by mass, still more preferably 80 to 100% by mass, further morepreferably 100% by mass, relative to the total amount (100% by mass) ofthe resin contained in the resin part (X).

From the viewpoint that the irregular concave portions are easy to formon the surface (α) of the resin layer to be formed, it is desirable thatthe resin part (X) contains a resin having a functional group, morepreferably an acrylic resin having a functional group.

In particular, in the case where the resin layer has a multilayerstructure formed by laminating a layer (Xβ), a layer (Y1) and a layer(Xα) in this order from the side on which a substrate or a releasematerial is provided, like in the pressure sensitive adhesive sheets 1 ato 2 b of FIG. 1, it is desirable from the above-mentioned viewpointsthat at least the layer (Y1) contains a resin having a functional group.

The functional group is a group to be a crosslinking start point with acrosslinking agent, and examples thereof include a hydroxy group, acarboxy group, an epoxy group, an amino group, a cyano group, a ketogroup, an alkoxysilyl group, etc., but a carboxyl group is preferred.

Also preferably, the resin part (X) further contains a crosslinkingagent along with the resin having a functional group. In particular, inthe case where the resin layer has the above-mentioned multilayerstructure, it is desirable that at least the layer (Y1) contains acrosslinking agent along with the above-mentioned, functionalgroup-having resin.

Examples of the crosslinking agent include an isocyanate crosslinkingagent, an epoxy crosslinking agent, an aziridine crosslinking agent, ametal chelate crosslinking agent, etc.

Examples of the isocyanate crosslinking agent include aromaticpolyisocyanates such as tolylene diisocyanate, diphenylmethanediisocyanate, xylylene diisocyanate, etc.; aliphatic polyisocyanatessuch as hexamethylene diisocyanate, etc.; alicyclic polyisocyanates suchas isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate,etc.; biuret forms and isocyanurate forms of these compounds, and adductforms that are reaction products with a low-molecular activehydrogen-containing compounds (ethylene glycol, propylene glycol,neopentyl glycol, trimethylolpropane, castor oil, etc.); etc.

Examples of the epoxy crosslinking agent include ethylene glycolglycidyl ether, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane,N,N,N′,N′-tetraglycidyl-m-xylylenediamine, 1,6-hexanediol diglycidylether, trimethylolpropane diglycidyl ether, diglycidylaniline,diglycidylamine, etc.

Examples of the aziridine crosslinking agent includediphenylmethane-4,4′-bis(1-aziridinecarboxamide),trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethanetri-β-aziridinylpropionate, toluene-2,4-bis(1-aziridinecarboxamide),triethylenemelamine, bisisophthaloyl-1-(2-methylaziridine),tris-1-(2-methylaziridine)phosphine,trimethylolpropanetri-β-(2-methylaziridine)propionate, etc.

The metal chelate crosslinking agent includes chelate compounds wherethe metal atom is aluminium, zirconium, titanium, zinc, iron, tin or thelike, and an aluminium chelate crosslinking agent is preferred.

Examples of the aluminium chelate crosslinking agent includediisopropoxyaluminium monooleyl acetacetate, monoisopropropoxyaluminiumbisoleyl acetacetate, monoisopropoxyalumiium monooleatemonoethylacetacetate, diisopropoxyaluminium monolauroyl acetacetate,diisopropoxyaluminium monostearyl acetacetate, diisopropoxyaluminiummonoisostearyl acetacetate, etc.

One alone or two or more of these crosslinking agents may be used eithersingly or as combined.

Among these, from the viewpoint that the irregular concave portions areeasy to form on the surface (α) of the resin layer to be formed, it isdesirable that the resin part (X) contains one or more selected from ametal chelate crosslinking agent, an epoxy crosslinking agent and anaziridine crosslinking agent, more preferably contains a metal chelatecrosslinking agent, and even more preferably contains an aluminiumchelate crosslinking agent.

The content of the crosslinking agent is preferably 0.01 to 15 parts bymass, and is more preferably 0.1 to 10 parts by mass, even morepreferably 0.3 to 7.0 parts by mass, relative to 100 parts by mass ofthe resin having a functional group.

From the viewpoint of bettering the shape retentive force of the pluralconcave portions on the surface (α) of the resin layer, it is desirablethat the resin part (X) contains both a metal chelate crosslinking agentand an epoxy crosslinking agent.

In the case where the resin part (X) contains both a metal chelatecrosslinking agent and an epoxy crosslinking agent, the content ratio bymass of the metal chelate crosslinking agent to the epoxy crosslinkingagent [metal chelate crosslinking agent/epoxy crosslinking agent], fromthe above-mentioned viewpoints, preferably 10/90 to 99.5/0.5, morepreferably 50/50 to 99.0/1.0, even more preferably 65/35 to 98.5/1.5,further more preferably 75/25 to 98.0/2.0.

The resin part (X) may contain any ordinary additive.

Examples of the ordinary additive include a tackifier, an antioxidant, asoftener (plasticizer), a rust inhibitor, a pigment, a dye, a retardant,a reaction accelerator, a UV absorbent, etc.

One alone or two or more of these ordinary additives may be used eithersingly or as combined.

In the case where these ordinary additives are contained, the content ofeach ordinary additive is preferably 0.0001 to 60 parts by mass, and ismore preferably 0.001 to 50 parts by mass, relative to 100 parts by massof the resin.

One alone or two or more resins may be contained in the resin part (X)either singly or as combined.

The forming material for the resin part (X) of the resin layer that thepressure sensitive adhesive sheet of the present invention has ispreferably a pressure sensitive adhesive containing a pressure sensitiveadhesive resin having a functional group, more preferably an acrylicpressure sensitive adhesive containing an acrylic resin (A) having afunctional group (hereinafter this may be simply referred to as “acrylicresin (A)”), and even more preferably an acrylic pressure sensitiveadhesive containing a functional group-having acrylic resin (A) and acrosslinking agent (B).

The acrylic pressure sensitive adhesive may be any of a solvent-type oneor an emulsion-type one.

The acrylic pressure sensitive adhesive favorable for the formingmaterial for the resin part (X) is described below.

Examples of the acrylic resin (A) contained in the acrylic pressuresensitive adhesive include a polymer having a structural unit derivedfrom an alkyl (meth)acrylate having a linear or branched alkyl group, apolymer having a structural unit derived from a (meth)acrylate having acyclic structure, etc.

The mass-average molecular weight (Mw) of the acrylic resin (A) ispreferably 50,000 to 1,500,000, more preferably 150,000 to 1,300,000,even more preferably 250,000 to 1,100,000, still more preferably 350,000to 900,000.

Preferably, the acrylic resin (A) contains an acrylic copolymer (A1)having a structural unit (a1) derived from an alkyl (meth)acrylate (a1′)having an alkyl group with 1 to 18 carbon atoms (hereinafter this may bereferred to as “monomer (a1′)”), and a structural unit (a2) derived froma functional group-containing monomer (a2′) (hereinafter this may bereferred to as “monomer (a2′)”), and more preferably contains an acryliccopolymer (A1).

The content of the acrylic copolymer (A1) is preferably 50 to 100% bymass, and is more preferably 70 to 100% by mass, even more preferably 80to 100% by mass, further more preferably 90 to 100% by mass, relative tothe total amount (100% by mass) of the acrylic resin (A) in the acrylicpressure sensitive adhesive.

The copolymerization morphology of the acrylic copolymer (A1) is notspecifically limited, and the copolymer may be any of a block copolymer,a random copolymer or a graft copolymer.

The carbon number of the alkyl group that the monomer (a1′) has is, fromthe viewpoint of improving pressure sensitive adhesion characteristics,more preferably 4 to 12, even more preferably 4 to 8, further morepreferably 4 to 6.

Examples of the monomer (a1′) include methyl (meth)acrylate, ethyl(meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate,2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl(meth)acrylate, stearyl (meth)acrylate, etc.

Among these, butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate arepreferred, and butyl (meth)acrylate is more preferred.

The content of the structural unit (a1) is preferably 50 to 99.5% bymass, and is more preferably 60 to 99% by mass, even more preferably 70to 95% by mass, still more preferably 80 to 93% by mass, relative to allthe structural units (100% by mass) of the acrylic copolymer (A1).

Examples of the monomer (a2′) include a hydroxy group-containingmonomer, a carboxy group-containing monomer, an epoxy group-containingmonomer, an amino group-containing monomer, a cyano group-containingmonomer, a keto group-containing monomer, an alkoxysilylgroup-containing monomer, etc.

Among these, a carboxy group-containing monomer is more preferred.

The carboxy group-containing monomer includes (meth)acrylic acid, maleicacid, fumaric acid, itaconic acid, etc., and (meth)acrylic acid ispreferred.

The content of the structural unit (a2) is preferably 0.5 to 50% bymass, and is more preferably 1 to 40% by mass, even more preferably 5 to30% by mass, still more preferably 7 to 20% by mass, relative to all thestructural units (100% by mass) of the acrylic copolymer (A1).

The acrylic copolymer (A1) may have a structural unit (a3) derived fromany other monomer (a3′) than the above-mentioned monomers (a1′) and(a2′).

Examples of the other monomer (a3′) include (meth)acrylates having acyclic structure such as cyclohexyl (meth)acrylate, benzyl(meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyloxyethyl(meth)acrylate, imido(meth)acrylate, etc.; vinyl acetate, acrylonitrile,styrene, etc.

The content of the structural unit (a3) is preferably 0 to 30% by mass,and is more preferably 0 to 20% by mass, even more preferably 0 to 10%by mass, still more preferably 0 to 5% by mass, relative to all thestructural units (100% by mass) of the acrylic copolymer (A1)

One alone or two or more of the above-mentioned monomers (a1′) to (a3′)may be used either singly or as combined.

A method for synthesis of the acrylic copolymer (A1) component is notspecifically limited. For example, the copolymer may be producedaccording to a method including dissolving starting monomers in asolvent and polymerizing them in a mode of solution polymerization inthe presence of a polymerization initiator, a chain transfer agent andthe like, or a method of emulsion polymerization in an aqueous systemusing starting monomers in the presence of an emulsifier, apolymerization initiator, a chain transfer agent, a dispersant, etc.

The crosslinking agent (B) to be contained in the acrylic pressuresensitive adhesive includes those mentioned hereinabove, but from theviewpoint of bettering pressure sensitive adhesion characteristics andfrom the viewpoint of facilitating the formation of the irregularconcave portions on the surface (α) of the resin layer to be formed, atleast one or more selected from a metal chelate crosslinking agent, anepoxy crosslinking agent and an aziridine crosslinking agent arepreferably contained, more preferably a metal chelate crosslinking agentis contained, and even more preferably an aluminium chelate crosslinkingagent is contained.

From the viewpoint of bettering the shape retentivity of plural concaveportions on the surface (α) of the resin layer, the crosslinking agent(B) preferably contains both a metal chelate crosslinking agent and anepoxy crosslinking agent.

The content of the crosslinking agent (B) is preferably 0.01 to 15 partsby mass, and is more preferably 0.1 to 10 parts by mass, even morepreferably 0.3 to 7.0 parts by mass, relative to 100 parts by mass ofthe acrylic resin (A) in the acrylic pressure sensitive adhesive.

In the case where a metal chelate crosslinking agent and an epoxycrosslinking agents are used as combined, the content ratio by mass ofthe metal chelate crosslinking agent to the epoxy crosslinking agent[metal chelate crosslinking agent/epoxy crosslinking agent] ispreferably 10/90 to 99.5/0.5, more preferably 50/50 to 99.0/1.0, evenmore preferably 65/35 to 98.5/1.5, further more preferably 75/25 to98.0/2.0.

The acrylic pressure sensitive adhesive to be used in one embodiment ofthe present invention may contain any ordinary additive within a rangenot detracting from the advantageous effects of the present invention.The general additive includes those mentioned hereinabove, and thecontent of the ordinary additive is also as mentioned above.

The acrylic pressure sensitive adhesive to be used in one embodiment ofthe present invention may contain any other pressure sensitive adhesiveresin than the acrylic resin (A) (for example, urethane resin, rubberresin, silicone resin, etc.) within a range not detracting from theadvantageous effects of the present invention.

The content of the acrylic resin (A) in the acrylic pressure sensitiveadhesive is preferably 50 to 100% by mass, and is more preferably 70 to100% by mass, even more preferably 80 to 100% by mass, still morepreferably 100% by mass, relative to the total amount (100% by mass) ofthe pressure sensitive adhesive resin contained in the acrylic pressuresensitive adhesive.

<Particle Part (Y)>

The particle part (Y) constituting the resin layer consists of fineparticles.

The mean particle size of the fine particles is, from the viewpoint ofimproving the air escape property and the blister resistance of thepressure sensitive adhesive sheet and from the viewpoint of facilitatingthe formation of the one or more irregular concave portions on thesurface (α) of the resin layer to be formed, preferably 0.01 to 100 morepreferably 0.05 to 25 μm, even more preferably 0.1 to 10 μm.

The fine particles to be used in one embodiment of the present inventionare not specifically limited, including inorganic particles such assilica particles, metal oxide particles, barium sulfate, calciumcarbonate, magnesium carbonate, glass beads, smectite and the like, andorganic particles such as acrylic beads, etc.

Among these fine particles, one or more selected from silica particles,metal oxide particles and smectite are preferred, and silica particlesare more preferred.

The silica particles that are used in one embodiment of the presentinvention may be any ones of dry-method silica and wet-method silica.

The silica particles that are used in one embodiment of the presentinvention may also be an organic-modified silica that has beensurface-modified with an organic compound having a reactive functionalgroup or the like, an inorganic-modified silica that has beensurface-treated with an inorganic compound such as sodium aluminate,sodium hydroxide or the like, as well as an organic/inorganic-modifiedsilica that has been surface-treated with any of these organic compoundsand inorganic compounds, or an organic/inorganic-modified silica thathas been surface-treated with an organic/inorganic hybrid material of asilane coupling agent, etc.

These silica particles may be in the form of a mixture of two or morekinds.

The mass concentration of silica in the silica particles is preferably70 to 100% by mass, and is more preferably 85 to 100% by mass, even morepreferably 90 to 100% by mass, relative to the total amount (100% bymass) of the silica particles.

The volume-average secondary particle diameter of the silica particlesthat are used in one embodiment of the present invention is, from theviewpoint of improving the air escape property and the blisterresistance of the pressure sensitive adhesive sheet, and from theviewpoint of facilitating the formation of the irregular concaveportions on the surface (α) of the resin layer to be formed, preferably0.5 to 50 μm, more preferably 0.5 to 30 still preferably 0.5 to 10 μm,still further preferably 1 to 8 μm, still further preferably 1.5 to 5μm.

In the present invention, the value of the volume-average secondaryparticle diameter of the silica particles is a value determined throughmeasurement of particle size distribution according to a Coulter countermethod using Multi sizer III or the like.

Examples of the metal oxide particles include particles of a metal oxideselected from titanium oxide, alumina, boehmite, chromium oxide, nickeloxide, copper oxide, titanium oxide, zirconium oxide, indium oxide, zincoxide, and composite oxides thereof, etc., and include sol particles ofthose metal oxides.

Examples of smectite include montmorillonite, beidellite, hectorite,saponite, stevensite, nontronite, sauconite, etc.

The mass retention rate after heating the resin layer that oneembodiment of the pressure sensitive adhesive sheet of the presentinvention has, at 800° C. for 30 minutes is preferably 3 to 90% by mass,more preferably 5 to 80% by mass, even more preferably 7 to 70% by mass,still more preferably 9 to 60% by mass.

The mass retention rate can be considered to indicate the content (% bymass) of the fine particles contained in the resin layer.

When the mass retention rate is 3% by mass or more, the pressuresensitive adhesive sheet can be excellent in air escape property andblister resistance. In addition, in production of the pressure sensitiveadhesive sheet of the present invention, plural concave portionssatisfying the requirements (1) to (111) can be readily formed on thesurface (α) of the resin layer to be formed. On the other hand, when themass retention rate is 90% by mass or less, a pressure sensitiveadhesive sheet can be provided in which the film strength of the resinlayer is high and which is excellent in water resistance and chemicalresistance.

[Production Method for Pressure Sensitive Adhesive Sheet]

Next, a method for producing the pressure sensitive adhesive sheet ofthe present invention is described.

The production method for the pressure sensitive adhesive sheet of thepresent invention is not specifically limited, but from the viewpoint ofproductivity and from the viewpoint of facilitating the formation of oneor more concave portions having irregular shapes through self-formationof the resin layer on the surface (α) of the resin layer, a methodhaving at least the following steps (1) and (2) is preferred.

Step (1): a step of forming a coating film (x′) formed by a composition(x) containing the resin as a main component, and a coating film (y′)formed by a composition (y) containing the fine particles,

Step (2): a step of drying the coating film (x′) and the coating film(y′) formed in the step (1) simultaneously.

<Step (1)>

The step (1) is a step of forming a coating film (x′) formed by thecomposition (x) containing the resin as a main component, and a coatingfilm (y′) formed by the composition (y) containing the fine particles.

The composition (x) is a forming material for the resin part (X), andpreferably contains a crosslinking agent along with the above-mentionedresin, and may further contain the above-mentioned ordinary additive.

The composition (y) is a forming material for the particle part (Y), andmay contain a resin and a crosslinking agent, as well as theabove-mentioned ordinary additive. The composition (y) containing thosecomponents of resin and others could also be a forming material for theresin part (X).

(Composition (x))

The resin contained in the composition (x) includes a resin thatconstitutes the above-mentioned resin part (X), and is preferably apressure sensitive adhesive resin having a functional group, morepreferably the above-mentioned functional group-having acrylic resin(A), and is preferably the above-mentioned acrylic copolymer (A1).

The content of the resin in the composition (x) is generally 40% by massor more, and is preferably 50% by mass or more, more preferably 65% bymass or more, even more preferably 75% by mass or more, still morepreferably 85% by mass or more, further more preferably 90% by mass ormore, relative to the total amount (100% by mass (but excluding diluentsolvent)) of the composition (x), and is preferably 100% by mass orless, more preferably 95% by mass or less, relative to the total amount(100% by mass (but excluding diluent solvent)) of the composition (x).

The crosslinking agent contained in the composition (x) includes thecrosslinking agent contained in the above-mentioned resin part (X).Preferably, one or more selected from a metal chelate crosslinking agentand an epoxy crosslinking agent are contained, and more preferably ametal chelate crosslinking agent is contained.

Further, from the viewpoint of bettering the shape retentivity of theplural concave portions on the surface (α) of the resin layer to beformed, it is desirable that the composition (x) contains both a metalchelate crosslinking agent and an epoxy crosslinking agent.

In the case where the composition (x) contains both a metal chelatecrosslinking agent and an epoxy crosslinking agent, the content ratio bymass of the metal chelate crosslinking agent to the epoxy crosslinkingagent in the composition (x) [metal chelate crosslinking agent/epoxycrosslinking agent] is preferably 10/90 to 99.5/0.5, more preferably50/50 to 99.0/1.0, even more preferably 65/35 to 98.5/1.5, still morepreferably 75/25 to 98.0/2.0.

The content of the crosslinking agent is preferably 0.01 to 15 parts bymass, and is more preferably 0.1 to 10 parts by mass, even morepreferably 0.3 to 7.0 parts by mass, relative to 100 parts by mass ofthe resin contained in the composition (x).

Preferably, the composition (x) is an acrylic pressure sensitiveadhesive containing the above-mentioned functional group-having acrylicresin (A) and crosslinking agent (B), more preferably an acrylicpressure sensitive adhesive containing the above-mentioned acryliccopolymer (A1) and crosslinking agent (B).

The details of the acrylic pressure sensitive adhesive are as mentionedabove.

The composition (x) may contain the above-mentioned fine particles, inwhich the content of the fine particles is less than 15% by mass and issmaller than the content of the resin contained in the composition (x).

Specifically, the content of the fine particles is less than 15% bymass, and is preferably 0 to 13% by mass, more preferably 0 to 10% bymass, even more preferably 0 to 5% by mass, still more preferably 0% bymass, relative to the total amount (100% by mass (but excluding diluentsolvent)) of the composition (x).

(Composition (y))

The composition (y) is a forming material for the particle part (Y), andcontains at least the above-mentioned fine particles in an amount of 15%by mass or more, but from the viewpoint of the dispersibility of thefine particles therein, the composition preferably contains a resinalong with the fine particles, and more preferably further contains acrosslinking agent along with the rein. The composition (y) may containany ordinary additive.

These resin, crosslinking agent and ordinary additive may be the formingmaterial for the resin part (X).

The fine particles to be contained in the composition (y) include thosementioned hereinabove, and from the viewpoint of forming the void part(Z) in the resin layer to provide a pressure sensitive adhesive sheethaving improved blister resistance, one or more kinds selected fromsilica particles, metal oxide particles and smectite are preferred.

The content of the fine particles in the composition (y) is, from theviewpoint of facilitating the formation of irregular concave portions onthe surface (α) of the resin layer through self-formation of the resinlayer, 15% by mass or more, and is preferably 20 to 100% by mass, morepreferably 25 to 90% by mass, even more preferably 30 to 85% by mass,still more preferably 35 to 80% by mass, relative to the total amount(100% by mass (but excluding diluent solvent)) of the resin composition(y).

The resin to be contained in the composition (y) includes the same onesas those of the resin to be contained in the above-mentioned composition(x), and preferably contains the same resin as in the composition (x).One alone or two or more of these resins may be used either singly or ascombined.

More specifically, the resin to be contained in the composition (y) ispreferably a resin having a functional group, more preferably theabove-mentioned functional group-having acrylic resin (A), even morepreferably the above-mentioned acrylic copolymer (A1).

The content of the resin in the composition (y) is generally 1 to 85% bymass, and is preferably 5 to 80% by mass, more preferably 10 to 75% bymass, even more preferably 20 to 70% by mass, further more preferably 25to 65% by mass, relative to the total amount (100% by mass (butexcluding diluent solvent)) of the composition (y).

The crosslinking agent to be contained in the composition (y) includesthose of the crosslinking agent to be contained in the above-mentionedresin part (X), but preferably the composition (y) contains at least oneor more selected from a metal chelate crosslinking agent and an epoxycrosslinking agent, more preferably a metal chelate crosslinking agent.Also preferably, the composition (y) contains both a metal chelatecrosslinking agent and an epoxy crosslinking agent.

In the case where the composition (y) contains both a metal chelatecrosslinking agent and an epoxy crosslinking agent, a preferred range ofthe content ratio (by mass) of the metal chelate crosslinking agent tothe epoxy crosslinking agent is the same as in the above-mentionedcomposition (x).

The content of the crosslinking agent is preferably 0.01 to 15 parts bymass, and is more preferably 0.1 to 10 parts by mass, even morepreferably 0.3 to 7.0 parts by mass, relative to 100 parts by mass ofthe resin contained in the composition (y).

(Formation Method for Coating Film (x′), (y′))

For facilitating the formation of a coating film, it is desirable that asolvent is incorporated in the composition (x) or (y) to give a solutionof the composition.

The solvent includes water, organic solvents, etc.

Examples of the organic solvent include toluene, ethyl acetate, butylacetate, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol,isopropyl alcohol, t-butanol, s-butanol, acetylacetone, cyclohexanone,n-hexane, cyclohexane, etc. One alone or two or more of these solventsmay be used either singly or as combined.

The order of laminating the coating films (x′) and (y′) to be formed inthis step is not specifically limited, but preferably, the coating film(x′) is laminated on the coating film (y′).

Regarding the formation method for the coating films (x′) and (y′),there may be employed a successive formation method of forming a coatingfilm (y′) and then forming a coating film (x′) on the coating film (y′),or from the viewpoint of productivity, there may also be employed asimultaneous coating method of coating with both the coating film (y′)and the coating film (x′) using a multilayer coater.

Examples of the coater for use in successive formation include a spincoater, a spray coater, a bar coater, a knife coater, a roll coater, aknife roll coater, a blade coater, a gravure coater, a curtain coater, adie coater, etc.

Examples of the coater for use in simultaneous coating with a multilayercoater include a curtain coater, a die coater, etc., and among these, adie coater is preferred from the viewpoint of operability.

In this step (1), after the formation of at least one of the coatingfilm (x′) and the coating film (y′) and prior to the step (2),pre-drying treatment may be carried out in such a degree that the curingreaction of the coating film could not go on.

The drying temperature in the pre-drying treatment in this step (1) isgenerally settled within a temperature range in which the formed coatingfilm is not cured, but is preferably lower than the drying temperaturein the step (2). A specific drying temperature indicated by thedefinition of indicating a range “lower than the drying temperature inthe step (2)” is preferably 10 to 45° C., more preferably 10 to 34° C.,even more preferably 15 to 30° C.

<Step (2)>

The step (2) is a step of drying the coating film (x′) and the coatingfilm (y′) formed in the step (1) simultaneously.

In this step, the coating film (x′) and the coating film (y′) formed aredried simultaneously, whereby a resin layer containing the resin part(X) and the particle part (Y) is formed and in addition, plural concaveportions are formed on the surface (α) of the resin layer.

The drying temperature in this step is, from the viewpoint offacilitating the formation of the one or more irregular concave portionsto be formed through self-formation of the resin layer on the surface(α) of the resin layer, preferably 35 to 200° C., more preferably 60 to180° C., even more preferably 70 to 160° C., still more preferably 80 to140° C.

When the drying temperature is 35° C. or higher, a pressure sensitiveadhesive sheet having good air escape property can be obtained. On theother hand, when the drying temperature is 200° C. or lower, thesubstrate and the release material that the pressure sensitive adhesivesheet has can be free from trouble of shrinkage thereof.

When the drying temperature is lower, the height difference of theconcave portions to be formed could increase but the number of theconcave portions to be formed tends to decrease.

In the vicinity of the particle part (Y) of the resin layer to be formedin this step, a void part (Z) may be formed.

The void part (Z) can be readily formed by using at least one or morekinds selected from silica particles, metal oxide particles and smectiteas the fine particles to be contained in the composition (y).

In the case where a pressure sensitive adhesive sheet having a resinlayer having a multilayer structure is produced in which the multilayerstructure is formed by laminating a layer (Xβ) mainly containing theresin part (X), a fine particle-containing layer (Y1) containing theparticle part (Y) in an amount of 15% by mass or more, and a layer (Xα)mainly containing the resin part (X) in this order, like the pressuresensitive adhesive sheets 1 a to 2 b of FIG. 1, a production method ofthe following first and second embodiments is preferred.

In the description of the production method of the following first andsecond embodiments, the “composition (xβ) or (xα) containing a resin asa main component” is the same as the above-mentioned composition (x),and the details of the constituent components contained in thecomposition (xβ) or (xα) (kind of the component, preferred components,content of the component, etc.) are also the same as in the latter. The“composition (y) containing fine particles in an amount of 15% by massor more” is also as mentioned above.

Production Method of First Embodiment

The production method of the first embodiment has at least the followingsteps (1A) and (2A).

Step (1A): a step of forming, on a substrate or a release material, acoating film (xβ′) of a composition (xβ) containing a resin as a maincomponent, a coating film (y′) of a composition (y) containing fineparticles in an amount of 15% by mass or more and a coating film (xα′)of a composition (xα) containing a resin as a main component, aslaminated thereon in this order

Step (2A): a step of drying the coating film (xβ′), the coating film(y′) and the coating film (xα′) formed in the step (1A) simultaneously

Also in the step (1A), it is desirable that the above-mentioned solventis incorporated in the composition (xβ), the composition (y) and thecomposition (xα) to form solutions of the individual compositions, andthe resultant solutions are used for coating.

Regarding the formation method for the coating film (xβ′), the coatingfilm (y′) and the coating film (xα′), there may be employed a successiveformation method of forming a coating film (xβ′) on a substrate or arelease material, then forming a coating film (y′) on the coating film(xβ′), and further forming a coating film (xα′) on the coating film(y′), using the above-mentioned coater, or a simultaneous coating methodof forming a coating film (xβ′), a coating film (y′) and a coating film(xα′), using the above-mentioned multilayer coater.

In the step (1A), after formation of one or more coating films of thecoating film (xβ′), the coating film (y′) and the coating film (xα′) andprior to the step (2A), pre-drying treatment may be carried out in sucha degree that the curing reaction of the coating films could not go on.

For example, after formation of the coating film (xβ′), the coating film(y′) and the coating film (xα′), such pre-drying treatment may becarried out every time after the formation, or after the formation ofthe coating film (xβ′) and the coating film (y′), the two may besubjected to the pre-drying treatment all together, and then the coatingfilm (xα′) may be formed thereon.

In this step (1A), the drying temperature for the pre-drying treatmentis generally so settled as to fall within a temperature range in whichthe formed coating film is not cured, but is preferably lower than thedrying temperature in the step (2A). A specific drying temperatureindicated by the definition of indicating a range “lower than the dryingtemperature in the step (2A)” is preferably 10 to 45° C., morepreferably 10 to 34° C., even more preferably 15 to 30° C.

The step (2A) is a step of drying the coating film (xβ), the coatingfilm (y′) and the coating film (xα′) formed in the step (1A),simultaneously. The preferred range of the drying temperature in thisstep is the same as that in the above-mentioned step (2). In this step,a resin layer containing the resin part (X) and the particle part (Y) isformed.

Production Method of Second Embodiment

The production method of the second embodiment has at least thefollowing steps (1B) and (2B).

Step (1B): a step of forming, on a layer (Xβ) mainly containing a resinpart (X) that is provided on a substrate or a release material, acoating film (y′) of a composition (y) containing fine particles in anamount of 15% by mass or more and a coating film (xα′) of a composition(xα) containing a resin as a main component, as laminated thereon inthis order

Step (2B): a step of drying the coating film (y′) and the coating film(xα′) formed in the step (1B) simultaneously

In the step (1B), the “layer (Xβ) mainly containing a resin part (X)” isformed by drying the above-mentioned coating film (xβ′) of a composition(xβ) containing a resin as a main component.

Since the layer (Xβ) is formed of the composition (xβ), the layer (Xβ)may contain a crosslinking agent, an ordinary additive and others inaddition to the resin therein. The content of the resin part (X) in thelayer (Xβ) is as described above.

Regarding the formation method for the layer (Xβ), a coating film (xβ′)of a composition (xβ) containing a resin as a main component is formedon a substrate or a release material, and the coating film (xβ′) isdried to form the layer.

The drying temperature at this time is not specifically limited, but ispreferably 35 to 200° C., more preferably 60 to 180° C., even morepreferably 70 to 160° C., still more preferably 80 to 140° C.

This embodiment differs from the above-mentioned first embodiment inthat the coating film (y′) and the coating film (xα′) are formed in thisorder on the layer (Xβ) formed by drying, but not on the coating film(xβ′).

Also in the step (1B), it is desirable that the above-mentioned solventis incorporated in the composition (y) and the composition (xα) to formsolutions of the respective compositions, and thereafter the solutionsare used for coating.

Regarding the formation method for the coating film (y′) and the coatingfilm (xα′), there may be employed a successive formation method offorming a coating film (y′) on the layer (Xβ) and then forming a coatingfilm (xα′) on the coating film (y′), using the above-mentioned coater,or a simultaneous coating method of coating with both the coating film(y′) and the coating film (xα′) using a multilayer coater.

In the step (1B), after formation of the coating film (y′) or afterformation of the coating film (y′) and the coating film (xα′) and priorto the step (2B), pre-drying treatment may be carried out in such adegree that the curing reaction of the coating films could not go on.

In this step (1B), the drying temperature for the pre-drying treatmentis generally so settled as to fall within a temperature range in whichthe formed coating film is not cured, but is preferably lower than thedrying temperature in the step (2B). A specific drying temperatureindicated by the definition of indicating a range “lower than the dryingtemperature in the step (2B)” is preferably 10 to 45° C., morepreferably 10 to 34° C., even more preferably 15 to 30° C.

The step (2B) is a step of drying the coating film (y′) and the coatingfilm (xα′) formed in the step (1B) simultaneously, and the preferredrange of the drying temperature in this step is the same as in theabove-mentioned step (2). In this step, a resin layer containing theresin part (X) and the particle part (Y) is formed.

(Viscoelastic Layer)

The present invention also provides a viscoelastic layer formed of amultilayer structure of 3 or more layers including a fineparticle-containing layer that contains fine particles, wherein the fineparticle-containing layer is formed not as the outermost layer of theviscoelastic layer, and one or more concave portions are formed on atleast one surface of the viscoelastic layer, and the shapes of the oneor more concave portions have irregular shapes.

One embodiment of the viscoelastic layer of the present inventionpreferably contains a resin part (X) containing a resin as a maincomponent and a particle part (Y) consisting of fine particles.

The kind and the content of the resin to constitute the viscoelasticlayer, the kind and the content of the fine particles, the kind and thecontent of other components, and the constituent elements relating tothe viscoelastic layer (layer configuration of the multilayer structure,elements relating to one or more concave portions, thickness, formingmaterial, production method, etc.) are the same as the constituentelements described hereinabove in the section of the resin layer.

However, the surface of the viscoelastic layer does not always need tohave pressure sensitive adhesiveness. Accordingly, the resin toconstitute the viscoelastic layer may be a non-pressure sensitiveadhesive resin alone.

EXAMPLES

The present invention will be described more specifically with referenceto the following examples, but the present invention is not limited tothe following examples. The property values in the following examplesand production examples are values measured by the following methods.

Mass Average Molecular Weight of Resin (Mw)

The measurement was performed by using a gel permeation chromatographyinstrument (“HLC-8020, a product name, produced by Tosoh Corporation)under the following conditions, and a value measured as the standardpolystyrene conversion was used. Measurement Condition

Column: “TSK guard column HXL-L”, “TSK gel G2500HXL”, “TSK gelG2000HXL”, and “TSK gel G1000HXL” (all produced by Tosoh Corporation),connected in series

Column temperature: 40° C.

Developing solvent: tetrahydrofuran Flow rate: 1.0 mL/min

Measurement of Volume Average Secondary Particle Diameter of SilicaParticles

The volume average secondary particle diameter of the silica particleswas obtained by measuring the particle size distribution with MultisizerIII (produced by Beckman Coulter Inc.) by the Coulter Counter method.

Measurement of Thickness of Resin Layer

The thickness of the resin layer was measured by observing the crosssection of the resin layer of the targeted pressure sensitive adhesivesheet with a scanning electron microscope (“S-4700”, a product name,produced by Hitachi, Ltd.).

Production Examples x-1 to x-6 Preparation of Solutions (x-1) to (x-6)of Resin Composition

To 100 parts by mass of the solution of an acrylic resin with the kindand the solid content shown in Table 1, a crosslinking agent and adiluting solvent with the kinds and the mixed amounts shown in Table 1were added, so as to prepare solutions (x-1) to (x-6) of a resincomposition having the solid contents shown in Table 1.

The details of the components shown in Table 1 used for the preparationof the solutions (x-1) to (x-6) of a resin composition are as follows.

Solution of Acrylic Resin

Solution (i): a mixed solution of toluene and ethyl acetate containingan acrylic resin (x-i) (an acrylic copolymer having structural unitsderived from butyl acrylate (BA) and acrylic acid (AA), BA/AA=90/10 (%by mass), Mw: 470,000) having a solid concentration of 33.6% by mass

Solution (ii): a mixed solution of toluene and ethyl acetate containingan acrylic resin (x-ii) (an acrylic copolymer having structural unitsderived from butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), vinylacetate (VAc), and acrylic acid (AA), BA/2EHA/VAc/AA=46/37/10/7 (% bymass), Mw: 370,000) having a solid concentration of 43.0% by mass

Crosslinking Agent

Aluminum chelate crosslinking agent: “M-5A”, a product name, produced bySoken Chemical & Engineering Co., Ltd., solid concentration: 4.95% bymass

Epoxy crosslinking agent: a solution of an epoxy crosslinking agentobtained by diluting “TETRAD-C” (a product name, produced by MitsubishiGas Chemical Co., Inc.) with toluene to make a solid concentration of 5%by mass

Isocyanate crosslinking agent: “Coronate L”, a product name, produced byTosoh Corporation, solid concentration: 75% by mass

Aziridine crosslinking agent: “BXX5134”, a product name, produced byToyochem Co., Ltd., solid concentration: 5% by mass

Diluting Solvent

IPA: isopropyl alcohol (IPA)

AcOEt: ethyl acetate

TABLE 1 Aluminum chelate Epoxy crosslinking crosslinking agent agent(TETRAD-C, (M-5A, solid con- solid concentration: centration: 4.95 wt %)5 wt %) Solid Solid content content per per 100 100 Solution of acrylicresin parts parts Mixed Mixed by Mixed by amount amount mass amount massof of of of of Mixed solid Mixed solid acrylic Mixed solid acrylicamount content amount content resin amount content resin Solution (part(part (part (part (part (part (part (part of resin by by by by by by byby composition Kind Kind of resin mass) mass) mass) mass) mass) mass)mass) mass) Pro- (x-1) solu- acrylic resin (x-i) 100 33.6 5 0.25 0.74 —— — duction tion (BA/AA = 90/10 Example (i) (wt %), Mw: x-1 470,000 Pro-(x-2) solu- acrylic resin (x-i) 100 33.6 — — — — — — duction tion (BA/AA= 90/10 Example (i) (wt %), Mw: x-2 470,000 Pro- (x-3) solu- acrylicresin (x-ii) 100 43.0 4.5 0.22 0.52 0.3 0.015 0.035 duction tion(BA/2EHA/ Example (ii) VAc/AA = x-3 46/37/10/7 (wt %), Mw: 370,000 Pro-(x-4) solu- acrylic resin (x-i) 100 33.6 — — — 0.6 0.030 0.089 ductiontion (BA/AA = 90/10 Example (i) (wt %), Mw: x-4 470,000 Pro- (x-5) solu-acrylic resin (x-i) 100 33.6 — — — — — — duction tion (BA/AA = 90/10Example (i) (wt %), Mw: x-5 470,000 Pro- (x-6) solu- acrylic resin (x-i)100 33.6 — — — — — — duction tion (BA/AA = 90/10 Example (i) (wt %), Mw:x-6 470,000 Aziridine crosslinking agent (BXX5134, solid concentration:5 wt %) Isocyanate crosslinking agent Mixed Solid (Coronate L, solidconcentration: 75 wt %) amount content Solid Solid of per concentrationcontent per Mixed solid 100 parts of solution Mixed Mixed 100 partsamount content by mass of of resin amount amount of by mass of (part(part acrylic resin Diluting composition (part by solid content acrylicresin by by (part by solvent (% by mass) (part by mass) (part by mass)mass) mass) mass) Kind mass) Pro- — — — — — — IPA 28 duction Example x-1Pro- — — — — — — IPA 27 duction Example x-2 Pro- — — — — — — IPA 34.4duction Example x-3 Pro- — — — — — — IPA 24 duction Example x-4 Pro- 1.50.56 1.674 — — — AcOET 28 duction Example x-5 Pro- — — — 1.0 0.050 0.149AcOET 28 duction Example x-6

Production Example y-0 Preparation of Fine Particle Dispersion Liquid(y-0)

To 100 parts by mass (solid content: 33.6 parts by mass) of the solution(i) containing the acrylic resin (x-i) (a mixed solution of toluene andethyl acetate containing an acrylic copolymer having structural unitsderived from butyl acrylate (BA) and acrylic acid (AA) (BA/AA=90/10 (%by mass), Mw: 470,000) having a solid concentration of 33.6% by mass),50.4 parts by mass (solid content: 50.4 parts by mass) of silicaparticles (“Nipsil E-200A”, a product name, produced by Tosoh SilicaCorporation, volume average secondary particle diameter: 3 μm) andtoluene were added, and the fine particles were dispersed, so as toprepare a fine particle dispersion liquid (y-0) having a solidconcentration of 30% by mass containing the acrylic resin and the silicaparticles.

Production Examples y-1 to y-8 Preparation of Coating Liquids (y-1) to(y-8) for Forming Coating Film (y′)

To the mixed amount shown in Table 2 of the fine particle dispersionliquid (y-0) produced in Production Example y-0, the kinds and the mixedamounts shown in Table 2 of the solution of an acrylic resin, thecrosslinking agent, and the diluting solvent were added, so as toprepare coating liquids (y-1) to (y-8) for forming a coating film (y′)having the solid concentrations shown in Table 2.

The details of the components shown in Table 2 used for the preparationof the coating liquids (y-1) to (y-8) for forming a coating film (y′)are as follows.

Solution of Acrylic Resin

Solution (i): acrylic resin (x-i) (the details thereof are describedabove)

Crosslinking Agent

Aluminum chelate crosslinking agent: “M-5A”, a product name, produced bySoken Chemical & Engineering Co., Ltd., solid concentration: 4.95% bymass

Epoxy crosslinking agent: a solution of an epoxy crosslinking agentobtained by diluting “TETRAD-C” (a product name, produced by MitsubishiGas Chemical Co., Inc.) with toluene to make a solid concentration of 5%by mass

Diluting Solvent

IPA: isopropyl alcohol

IPA/CHN: mixed solvent containing isopropyl alcohol (IPA) andcyclohexanone (CHN) (IPA/CHN=60/40 (mass ratio))

TABLE 2 Aluminum chelate Expoxy Con- Fine particle crosslinking agentcrosslinking agent cen- dispersion (M-5A, (TETRAD-C, solid tra- liquidsolid concen- concentration: tion (y-0) produced tration: 4.95 wt %) 5wt %) of in Production Solid Sol- fine Example con- id par- y-0 (solidtent con- ticles concentration: per tent in 30 100 per solid wt %)Solution of acrylic resin Mix- parts Mix- 100 Solid con- Coat- MixedCon- Mixed ed by ed parts con- tent ing a- tent a- a- mass a- by cen- ofliq- mount of mount mount of mount mass tra- coat- uid Mix- of fine Mix-of Mix- of a- Mix- of of tion ing for ed solid par- ed solid ed solidcryl- ed solid acryl- Di- of liq- for- a- con- ticles a- con- a- con- ica- con- ic lut- coat- uid ming mount tent (*) mount tent mount tentresin mount tent resin ing ing (**) coated (part (part (part (part (part(part (part (part (part (part (part sol- liquid (% layer by by by Kindby by by by by by by by vent (% by by (y′) mass) mass) mass) Kind orresin mass) mass) mass) mass) mass) mass) mass) mass) Kind mass) mass)Pro- (y-1) 69.7 20.9 12.5 solu- acrylic 30.3 10.2 5.52 0.27 1.47 — — —IPA 27 40 duc- tion resin tion (i) (x-i) Ex- (BA/ am- AA = ple 90/10 y-1(wt %), Mw: 470,000 Pro- (y-2) 61.6 18.5 11.1 solu- acrylic 38.4 12.96.04 0.30 1.47 — — — IPA 27 35 duc- tion resin tion (i) (x-i) Ex- (BA/am- AA = ple 90/10 y-2 (wt %), Mw: 470,000 Pro- (y-3) 77.6 23.3 14.0solu- acrylic 22.4 7.5 5.01 0.25 1.47 — — — IPA 27 45 duc- tion resintion (i) (x-i) Ex- (BA/ am- AA = ple 90/10 y-3 (wt %), Mw: 470,000 Pro-(y-4) 85.4 25.6 15.4 solu- acrylic 14.6 4.9 4.51 0.22 1.47 — — — IPA 2750 duc- tion resin tion (i) (x-i) Ex- (BA/ am- AA = ple 90/10 y-4 (wt%), Mw: 470,000 Pro- (y-5) 71.0 21.3 12.8 solu- acrylic 29.0 9.7 5.440.27 1.47 — — — IPA/ 26 41 duc- tion resin CHN tion (i) (x-i) Ex- (BA/am- AA = ple 90/10 y-5 (wt %), Mw: 470,000 Pro- (y-6) 69.7 20.9 12.5solu- acrylic 30.3 10.2 — — — — — — IPA 27 40 duc- tion resin tion (i)(x-i) Ex- (BA/ am- AA = ple 90/10 y-6 (wt %), Mw: 470,000 Pro- (y-7)71.0 21.3 12.8 solu- acrylic 29.0 9.7 — — — 0.66 0.033 0.18 IPA 26 41duc- tion resin tion (i) (x-i) Ex- (BA/ am- AA = ple 90/10 y-7 (wt %),Mw: 470,000 Pro- (y-8) 71.0 21.3 12.8 solu- acrylic 29.0 9.7 2.72 0.130.74 0.33 0.017 0.09 IPA 26 41 duc- tion resin tion (i) (x-i) Ex- (BA/am- AA = ple 90/10 y-8 (wt %), Mw: 470,000 (*): value calculated from(solid mixed amount), × 50.4/(50.4 + 33.3) (**): value cabulated from(content of fine particles)/((solid mixed amount in fine particledispersion liquid (y-0)) + (solid mixed amount of acrylic resin) +(solid mixed amount of aluminum chelate crosslinking agent) + (solidmixed amount of epoxy crosslinking agent)) × 100

Examples 1 to 8

(1) Formation of Coating film

A polyethylene terephthalate (PET) film having an aluminum vapordeposition layer on one surface thereof (“FNS MAT N50”, a product name,produced by Lintec Corporation, thickness: 50 μm) was used as asubstrate.

On the aluminum vapor deposition layer of the PET film, the solution(x-1) of a resin composition prepared in Production Example x-1 wascoated with an applicator to the thickness shown in Table 3 as thethickness of the coating film after coating (i.e., the thickness of thecoating film in a non-dried state), so as to form a coating film (xβ′).

Subsequently, on the coating film (xβ′) thus formed, one of the coatingliquids (y-1) to (y-4) for forming a coating film (y′) of the kindsshown in Table 3 was coated with an applicator to the thickness shown inTable 3 as the total thickness after coating both the two layers, i.e.,the coating film (xβ′) and a coating film (y′) (i.e., the totalthickness of the two layers in a non-dried state), so as to form acoating film (y′).

Then, on the coating film (y′) thus formed, the solution (x-1) of aresin composition prepared in Production Example x-1 was coated with anapplicator to the thickness shown in Table 3 as the total thicknessafter coating all the three layers, i.e., the coating film (xβ′), thecoating film (y′), and a coating film (xα′) (i.e., the total thicknessof the three layers in a non-dried state), so as to form a coating film(xα′).

(2) Drying Treatment

The three layers of the coating film (xβ′), the coating film (y′), andthe coating film (xα′) were simultaneously dried at a drying temperatureof 100° C. for 2 minutes, thereby producing a pressure sensitiveadhesive sheet, having a resin layer containing a resin part (X) and aparticle part (Y) having the thickness shown in Table 3.

Example 9

A PET film having an aluminum vapor deposition layer on one surfacethereof (“FNS MAT N50”, a product name, produced by Lintec Corporation,thickness: 50 μm) was used as a substrate.

On the aluminum vapor deposition layer of the PET film, the solution(x-2) of a resin composition prepared in Production Example x-2 wascoated with a knife coater to a thickness of 25 μm as the thickness ofthe coating film after coating (i.e., the thickness of the coating filmin a non-dried state), so as to form a coating film (xβ′), which wasthen dried at a drying temperature of 100° C. for 2 minutes, so as toform a layer (Xβ) containing a resin part (X).

Lamination was performed in such a manner that the surface of the layer(Xβ) thus formed was attached to a release agent layer of a release film(“SP-PET381031”, a product name, produced by Lintec Corporation, a PETfilm having a silicone release agent layer provided on one surfacethereof, thickness: 38 μm), so as to produce once a laminated bodyhaving the layer (Xβ).

Subsequently, on the surface of the layer (Xβ) having been exposed byremoving the release film of the laminated body, the coating liquid(y-1) for forming a coating film (y′) prepared in Production Example y-1and the solution (x-1) of a resin composition prepared in ProductionExample x-1 were simultaneously coated with a multilayer die coater(width: 500 mm), so as to form a coating film (y′) and a coating film(xα′) simultaneously in this order on the layer (Xβ). The coated layerswere formed to a thickness of 55 μm for the coating film (y′) and athickness of 65 μm for the coating film (xα′) through the setting of themultilayer die coater.

Then, the two layers of the coating film (y′) and the coating film (xα′)were simultaneously dried at a drying temperature of 100° C. for 2minutes, thereby producing a pressure sensitive adhesive sheet, having aresin layer containing a resin part (X) and a particle part (Y) havingthe thickness shown in Table 3.

Comparative Example 1

A pressure sensitive adhesive sheet having a resin layer containing onlya resin part (X) having a thickness of 25 μm was produced in the samemanner as in Example 1, except that the coating film (y′) and thecoating film (xα′) in Example 1 were not formed, but on the aluminumvapor deposition layer of the PET film used as the substrate, thesolution (x-1) of a resin composition prepared in Production Example x-1was coated with a knife coater to a thickness of 25 μm after drying toform a coating film (xβ′).

Comparative Example 2

A PET film having an aluminum vapor deposition layer on one surfacethereof (“FNS MAT N50”, a product name, produced by Lintec Corporation,thickness: 50 μm) was used as a substrate.

On the aluminum vapor deposition layer of the PET film, the solution(x-1) of a resin composition prepared in Production Example x-1 wascoated with an applicator to form a coating film (0), which was thendried at 100° C. for 2 minutes, so as to form a layer (Xβ) containing aresin part (X) having a thickness of 5 μm.

Separately from the above, on a release agent layer of a release film(“SP-PET381031”, a product name, produced by Lintec Corporation, a PETfilm having a silicone release agent layer provided on one surfacethereof, thickness: 38 μm), the coating liquid (y-1) for forming acoating film (y′) prepared in Production Example y-1 was coated with anapplicator to form a coated layer (y′), which was then dried at 100° C.for 2 minutes, so as to form a layer (Y1) containing a resin part (X)and a particle part (Y) having a thickness of 15 μm.

Further separately from the above, on a release agent layer of a releasefilm of the same kind as above, the solution (x-1) of a resincomposition prepared in Production Example x-1 was coated with anapplicator to form a coating film (xα′), which was then dried at 100° C.for 2 minutes, so as to form a layer (Xα) containing a resin part (X)having a thickness of 5 μm.

Then, lamination was performed in such a manner that the surface of thelayer (Xβ) formed on the PET film as the substrate was attached to theexposed surface of the layer (Y1) thus formed. Furthermore, laminationwas performed in such a manner that the surface of the layer (Y1) havingbeen exposed by removing the release film on the layer (Y1) was attachedto the exposed surface of the layer (Xα) thus formed.

According to the procedures, a pressure sensitive adhesive sheet havinga resin layer containing a resin part (X) and a particle part (Y) havinga thickness of 25 μm, containing the substrate having laminated in thisorder thereon the layer (Xβ), the layer (Y1), and the layer (Xα) wasproduced.

Examples 10 to 16

A PET film having an aluminum vapor deposition layer on one surfacethereof (“FNS MAT N50”, a product name, produced by Lintec Corporation,thickness: 50 μm) was used as a substrate.

On the aluminum vapor deposition layer of the PET film, one of thesolutions (x-1) to (x-6) of a resin composition prepared in ProductionExamples x-1 to x-6 and one of the coating liquids (y-1) to (y-8) forforming a coating film (y′) prepared in Production Examples y-1 to y-8were simultaneously coated with a multilayer die coater (width: 250 mm)at the flow rate and the coating speed shown in Table 4, so as to form acoating film (xβ′), a coating film (y′), and a coating film (xα′)simultaneously in this order from the side of the substrate.

The kind of the solution of the resin composition and the kind of thecoating liquid for forming a coated layer (y′) used as formationmaterials of the coating films are shown in Table 4.

The three layers of the coating film (xβ′), the coating film (y′), andthe coating film (xα′) were simultaneously dried at a drying temperatureof 100° C. for 2 minutes, thereby producing a pressure sensitiveadhesive sheet, having a resin layer containing a resin part (X) and aparticle part (Y) having the thickness shown in Table 4.

Example 17

On a release agent layer of a release film (“SP-PET381031”, a productname, produced by Lintec Corporation, a PET film having a siliconerelease agent layer provided on one surface thereof, thickness: 38 μm)as a first release material, the solution (x-3) of a resin compositionprepared in Production Example x-3, the coating liquid (y-5) for forminga coating film (y′) prepared in Production Example y-5, and the solution(x-3) of a resin composition prepared in Production Example x-3 weresimultaneously coated in this order with a multilayer die coater (width:250 mm) at the flow rate and the coating speed shown in Table 4, so asto form a coating film (xβ′), a coating film (y′), and a coating film(xα′) simultaneously in this order from the side of the release film.

Then, the three layers of the coating film (xβ′), the coating film (y′),and the coating film (xα′) were simultaneously dried at a dryingtemperature of 100° C. for 2 minutes, so as to form a resin layercontaining a resin part (X) and a particle part (Y) having the thicknessshown in Table 4. Then, lamination was performed in such a manner thatthe surface (α) of the resin layer thus formed was attached to a surfaceof a release agent layer of a release film (“SP-PET386040”, a productname, produced by Lintec Corporation) as a second release material,thereby producing a pressure sensitive adhesive sheet without asubstrate.

Subsequently, after allowing to stand the pressure sensitive adhesivesheet without a substrate under an environment at 23° C. for one week,the first release material was removed, and lamination was performed insuch a manner that the exposed surface (β) of the resin layer wasattached to a surface of an aluminum vapor deposition layer of a PETfilm having an aluminum vapor deposition layer (“FNS MAT N50”, a productname, produced by Lintec Corporation, thickness: 50 μm) as a substrate,thereby providing a pressure sensitive adhesive sheet with a substrate.

Example 18

A PET film having an aluminum vapor deposition layer on one surfacethereof (“FNS MAT N50”, a product name, produced by Lintec Corporation,thickness: 50 μm) was used as a substrate.

On the aluminum vapor deposition layer of the PET film, the solution(x-1) of a resin composition prepared in Production Example x-1 wascoated with a knife coater to form a coating film (xβ′), which was thendried at 100° C. for 2 minutes, so as to form a layer (Xβ) containing aresin part (X) having a thickness of 8 μin. Lamination was performed insuch a manner that the surface of the layer (Xβ) thus formed wasattached to a surface of a release agent layer of a release film(“SP-PET381031”, a product name, produced by Lintec Corporation, a PETfilm having a silicone release agent layer provided on one surfacethereof, thickness: 38 μm), so as to produce once a laminated bodyhaving the layer (Xβ).

Subsequently, on the surface of the layer (xβ) having been exposed byremoving the release film of the laminated body, the coating liquid(y-1) for forming a coating film (y′) prepared in Production Example y-1and the solution (x-1) of a resin composition prepared in ProductionExample x-1 were simultaneously coated in this order with a multilayerdie coater (width: 500 mm) at the flow rate and the coating speed shownin Table 4, so as to form a coating film (y′) and a coating film (xα′)simultaneously in this order from the side of the layer (Xβ).

Then, the two layers of the coating film (y′) and the coating film (xα′)were simultaneously dried at a drying temperature of 100° C. for 2minutes, thereby producing a pressure sensitive adhesive sheet having aresin layer containing a resin part (X) and a particle part (Y) havingthe thickness shown in Table 4.

The resin layer of each pressure sensitive adhesive sheet produced inExamples and Comparative Examples was checked for the presence orabsence of concave portions on the surface (α), the presence or absenceof irregular shapes of the concave portions, the shape and the positionof the concave portions on the surface (α), the shape of the attachedface, and the mass retention rate of the resin layer, according to themethods mentioned below. The results are shown in Table 3 and Table 4.

<Presence or Absence of One or More Irregular Concave Portions onSurface (α)>

Ten regions (R) each surrounded by a square having an edge length of 4mm were arbitrarily selected on the surface (α) of the resin layer ofthe pressure sensitive adhesive sheet produced in Examples andComparative Examples, and the shapes of the one or more concave portionsexisting in each region (R) were observed visually or with a digitalmicroscope (trade name “Digital Microscope VHX-5000, manufactured byKeyence Corporation, magnification: 50), in a planar view (and ifdesired, in a stereoscopic view) from the side of the surface (α) tothereby confirm the presence or absence of irregular concave portions.

In the case where plural concave portions were confirmed in the selected10 regions by the above-mentioned observation, the number of the concaveportions, the presence or absence of periodicity of the positions of theconcave portions (requirement (IV)) and the shape of the attached facewere also confirmed.

<Shapes of One or More Concave Portions on Surface (α)>

The specific region defined by the requirement on the surface (α) of theresin layer of the pressure sensitive adhesive sheet was checked for thepresence or absence of one or more concave portions satisfying thefollowing requirements (I) to (III) using a scanning electron microscope(trade name “S-4700” manufactured by Hitachi Limited; for therequirement (II), with a magnification of 30).

In Table 3 and Table 4, the samples judged to have one or more concaveportions satisfying the requirements were given “A”, while those judgednot to have one or more concave portions satisfying the requirementswere given “F”.

Requirement (I): Plural concave portions having a maximum heightdifference of 0.5 μm or more exist in a region (P) surrounded by a 5-mmsquare arbitrarily selected on the surface (α).

Requirement (II): Plural concave portions having a maximum heightdifference of 0.5 μm or more exist in a region (P) surrounded by a 5-mmsquare arbitrarily selected on the surface (α), and relative to thetotal number (100%) of the plural concave portions, the number of theconcave portions having shapes differing from each other is 95% or more(in the case of 100%, that is, in the case where all the concaveportions in the region (P) have shapes differing from each other, thesamples are given “A+” in the Tables).

Requirement (III): One or more concave portions having a maximum heightdifference of 0.5 μm or more exist in a region (Q) surrounded by a 1-mmsquare arbitrarily selected on the surface (α).

Of the height difference values of the plural concave portions measuredin evaluation for the requirement (I), the largest value is shown as“maximum height difference” in Table 3 and Table 4.

Mass Retention Rate of Resin Layer of Pressure Sensitive Adhesive Sheet

For Examples and Comparative Examples except for Example 17, the resinlayer was formed according to the method of the Examples and ComparativeExamples on the surface of the release agent layer of a release film(“SP-PET381031”, a product name, produced by Lintec Corporation, a PETfilm having a silicone release agent layer provided on one surfacethereof, thickness: 38 μm) instead of the substrate, and then therelease film was removed, so as to provide a sole resin layer.

For Example 17, the two release films were removed from the pressuresensitive adhesive sheet without a substrate obtained in the course ofthe production, so as to provide a sole resin layer.

The resin layer before heating was measured for the mass thereof, andthen heated to 800° C. for 30 minutes in a muffle furnace (“KDF-P90”, aproduct name, produced by Denken Co., Ltd.). The resin layer afterheating was measured for the mass thereof, and the mass retention rateof the resin layer was calculated by the following expression.

mass retention rate of resin layer (%)=((mass of resin layer afterheating)/(mass of resin layer before heating))×100

The pressure sensitive adhesive sheets produced in Examples andComparative Examples were measured or evaluated for the “air escapeproperty”, the “blister resistance”, and the “adhesive strength”according to the following methods. The results are shown in Tables 3and 4.

Air Escape Property

The pressure sensitive adhesive sheet in a size of 50 mm in length and50 mm in width was attached to a melamine-coated plate as an adherend ina manner forming air accumulation. The presence of absence of the airaccumulation after press-attaching with a squeegee was observed, and theair escape property of the pressure sensitive adhesive sheets wasevaluated based on the following standard.

A: The air accumulation disappeared, and excellent air escape propertywas obtained.

F: The air accumulation remained, and poor air escape property wasobtained.

Blister Resistance

The pressure sensitive adhesive sheet in a size of 50 mm in length and50 mm in width was attached to a polymethyl methacrylate plate having asize of 70 mm in length, 150 mm in width, and 2 mm in thickness(“Acrylite L001”, produced by Mitsubishi Rayon Co., Ltd.), followed bypress-attaching with a squeegee, so as to provide a test specimen.

The test specimen was allowed to stand at 23° C. for 12 hours, thenallowed to stand in a hot air dryer at 80° C. for 1.5 hours, furtherallowed to stand in a hot air dryer at 90° C. for 1.5 hours, and thenvisible to the naked eyes for the occurrence state of blister after theheat acceleration, and the blister resistance of the pressure sensitiveadhesive sheets was evaluated based on the following standard.

A: Completely no blister was observed.

B: Blister was partially observed.

C: Blister was observed over the surface.

Adhesive Strength

The pressure sensitive adhesive sheets produced in Examples andComparative Examples were cut into a size of 25 mm in length and 300 mmin width, and the surface (α) of the resin layer of the pressuresensitive adhesive sheets was attached to a stainless steel plate(SUS304, polished with #360 polishing paper) under an environment of 23°C., 50% RH (relative humidity), followed by allowing to stand in thesame environment for 24 hours. After standing, the adhesive strength ofthe pressure sensitive adhesive sheets was measured according to JISZ0237:2000 by the 180° peeling method at a peeling speed of 300 mm/min.

TABLE 3 Coating film (y′) Fine Par- ticle Resin layer con- Shapes of oneor more concave Mass Thickness of cen- portions on surface (α) re-Pressure sensitive coating Coat- tration Coat- ten- adhesive sheet film(μm) ing in ing Num- Sha- Maxi- tion evaluation Items Coat- film coat-film ber pes mum rate Ad- Coat- ing (xβ′) Kind ing (xα′) of of height ofAir Blis- hesive Coat- ing film Kind of film Kind con- con- Re- Re- Re-Re- dif- resin es- ter stren- ing film (xβ′ + of coat- (y′) of Thick-cave cave quire- quire- quire- quire- fer- layer cape re- gth film(xβ′ + y′ + solu- ing (mass solu- ness por- por- ment ment ment mentence (mass prop- sis- (N/25 (xβ′) y′) xα′) tion liquid %) tion (μm)tions tions (I) (II) (III) (IV) (μm) %) erty tance mm) Ex- 25.0 75.0 100(x-1) (y-1) 40 (x-1) 25.7 plu- irreg- A A+ A no 15.7 16.9 A A 8.6 am-ral ular ple 1 Ex- 12.5 75.0 100 (x-1) (y-1) 40 (x-1) 25.1 plu- irreg- AA+ A no 17.3 20.0 A A 12.7 am- ral ular ple 2 Ex- 25.0 50.0 100 (x-1)(y-1) 40 (x-1) 23.9 plu- irreg- A A+ A no 7.6 9.5 A A 11.7 am- ral ularple 3 Ex- 25.0 200 250 (x-1) (y-1) 40 (x-1) 43.1 plu- irreg- A A+ A no42.4 28.1 A A 7.8 am- ral ular ple 4 Ex- 25.0 75.0 100 (x-1) (y-2) 35(x-1) 23.8 plu- irreg- A A+ A no 6.6 15.0 A A 9.4 am- ral ular ple 5 Ex-25.0 75.0 100 (x-1) (y-3) 45 (x-1) 30.1 plu- irreg- A A+ A no 26.3 20.9A A 10.1 am- ral ular ple 6 Ex- 25.0 75.0 100 (x-1) (y-4) 50 (x-1) 32.3plu- irreg- A A+ A no 30.8 23.1 A A 10.8 am- ral ular ple 7 Ex- 25.0 200250 (x-1) (y-2) 35 (x-1) 41.0 plu- irreg- A A+ A no 3.5 21.3 A A 12.4am- ral ular ple 8 Ex- 25.0 80⁽*¹⁾ 145⁽*¹⁾ (x-2) (y-1) 40 (x-1) 42.0plu- irreg- A A+ A no 18.5 15.1 A A 10.2 am- ral ular ple 9 Com- 25⁽*²⁾— — (x-1) — 0 — 25.0 no — F -⁽*³⁾ F — 0 0.0 F C 18.0 par- ative Ex- am-ple 1 Com- 25⁽*²⁾ 20⁽*²⁾ 25⁽*²⁾ (x-1) (y-1) 40 (x-1) 25.0 no — F -⁽*³⁾ F— 0 17.0 F A 15.0 par- ative Ex am- ple 2 ⁽*¹⁾This is not a measuredvalue but the thickness of the coating film preset in the multilayer diecoater. ⁽*²⁾This is the thickness of the coating film after dried.⁽*³⁾No concave portion was formed on the surface (α), and the sample wasnot evaluated.

TABLE 4 Flow rate of solution Coating film (y′) (coating liquid) (g/min)Fine particle Coating Coat- Coat- Coat- Coating concentration Coatingspeed ing ing ing film (xβ′) Kind of in coating film (xα′) (m/ film filmfilm Kind of coating film (y′) Kind of min) (xβ′) (y′) (xα′) solutionliuid (mass %) solution Example 10 3.0 27 27 27 (x-1) (y-1) 40 (x-1)Example 11 3.0 27 21 27 (x-1) (y-1) 40 (x-1) Example 12 3.0 27 9 27(x-1) (y-1) 40 (x-1) Example 13 3.0 27 51 54 (x-3) (y-5) 41 (x-3)Example 14 3.0 27 27 27 (x-4) (y-6) 40 (x-4) Example 15 3.0 27 27 27(x-4) (y-7) 40 (x-4) Example 16 3.0 27 27 27 (x-5) (y-8) 40 (x-6)Example 17 3.0 27 51 54 (x-3) (y-5) 41 (x-3) Example 18 5.0 (8 μm)⁽*⁴⁾133 161 (x-1) (y-1) 40 (x-1) Resin layer shapes of one or more concaveportions of surface (α) Mass Pressure sensitive adhesive Number ShapesRe- Re- Re- Re- Maximum retention sheet evaluation Items Thick- of ofquire- quire- quire- quire- height rate of Air Adhesive ness concaveconcave ment ment ment ment difference resin layer escape Blisterstrength (μm) portions portions (I) (II) (III) (IV) (μm) (mass %)property resistance (N/25 mm) Example 10 30.0 pulral irregular A A+ A no20.3 8.6 A A 8.8 Example 11 26.7 pulral irregular A A+ A no 15.0 7.1 A A10.8 Example 12 23.3 pulral irregular A A+ A no 10.6 5.8 A A 13.3Example 13 51.0 pulral irregular A A+ A no 42.5 12.6 A A 23.5 Example 1429.6 pulral irregular A A+ A no 19.5 8.4 A A 10.3 Example 15 29.2 pulralirregular A A+ A no 19.2 8.2 A A 11.6 Example 16 29.5 pulral irregular AA+ A no 17.7 8.0 A A 9.8 Example 17 51.0 pulral irregular A A+ A no 41.012.6 A A 24.0 Example 18 42.0 pulral irregular A A+ A no 18.5 15.1 A A10.2 ⁽*⁴⁾This is the thickness of the coaling film (xβ′) after dried.

From Table 3 and Table 4, it is confirmed that the pressure sensitiveadhesive sheets produced in Examples 1 to 18 all had, on the surface (α)thereof, concave portions satisfying the above-mentioned requirements(I) to (III) and formed through self-formation of the resin layer, andthese pressure sensitive adhesive sheets all had good air escapeproperty, blister resistance and pressure sensitive adhesiveness.

In all of the pressure sensitive adhesive sheets produced in Examples 1to 18, when the region (P) on the surface (α) was observed with theabove-mentioned scanning electron microscope (magnification: 30), theshapes of the plural concave portions had irregular shapes, and did nothave any predetermined pattern, and it was confirmed that these concaveportions were not formed through embossed pattern transfer. In addition,it was confirmed that, in a cross section in the thickness direction ofthe resin layer, the boundary between the fine particle-containing layerand the other layer was not parallel to the horizontal plane of thesubstrate or the release material, and the fine particle-containinglayer had, as existing therein intermittently relative to the horizontalplane direction of the substrate or the release material, a part denselycontaining fine particles and a part not containing fine particles.Further, the irregular shapes of the concave portions existing on thesurface (α) were visually confirmed from the side of the exposed surface(α).

In addition, the shape of the attached face existing inside the region(P) on the surface (α) also had an irregular shape.

In addition, it was confirmed that, in all the pressure sensitiveadhesive sheets produced in Examples 1 to 18, one or more concaveportions existing in the region (Q) on the surface (α) of the resinlayer extended toward any side of a 1-mm square that is a boundary lineof the region (Q), and further extended continuously in the other region(Q′) surrounded by a square having an edge length of 1 mm, which isadjacent to the region (Q). This can be confirmed also from the obliqueimage of the surface (α) of the resin layer in FIG. 4(b) and FIG. 5(b).

FIG. 4 and FIG. 5 each include images of the pressure sensitive adhesivesheet produced in Example 1 and Example 10, respectively, taken througha scanning electron microscope; and (a) is an image of a cross sectionof the pressure sensitive adhesive sheet, and (b) is a perspective imageof the surface (α) of the resin layer of the pressure sensitive adhesivesheet. In the image of FIG. 4(a), 10 scale marks given at the bottomright of the image indicate a length of 20.0 μm, and in the image ofFIG. 4(b), 10 scale marks given at the bottom right of the imageindicate a length of 1.00 mm. In the image of FIG. 5(a), 10 scale marksgiven at the bottom right of the image indicate a length of 200 μm, andin the image of FIG. 5(b), 10 scale marks given at the bottom right ofthe image indicate a length of 1.00 mm.

The images of FIG. 4 and FIG. 5 show the shapes of the concave portionsexisting on the surface (α) of the resin layer of the pressure sensitiveadhesive sheet produced in Examples 1 and 10, respectively. Thecross-sectional profiles of the concave portions of the pressuresensitive adhesive sheets of other Examples and the shapes of theconcave portions observed from the side of the surface (α) of the resinlayer thereof were all the same as in the images shown in FIG. 4 andFIG. 5.

On the other hand, formation of any specific concave portions could notbe recognized on the surface of the resin layer that the pressuresensitive adhesive sheet produced in Comparative Examples 1 and 2 has,and the air escape property of these pressure sensitive adhesive sheetswas poor. In addition, the pressure sensitive adhesive sheet ofComparative Example 1 was also poor in blister resistance.

FIG. 6 includes images of the pressure sensitive adhesive sheet producedin Comparative Example 1, taken through a scanning electron microscope;and (a) of FIG. 6 is an image of a cross section of the pressuresensitive adhesive sheet, and (b) of FIG. 6 is a perspective image ofthe surface (α) of the resin layer of the pressure sensitive adhesivesheet. In the image of FIG. 6(a), 10 scale marks given at the bottomright of the image indicate a length of 20.0 μm, and in the image ofFIG. 6(b), 10 scale marks given at the bottom right of the imageindicate a length of 1.00 mm.

As shown in FIG. 6, formation of concave portions was not seen on thesurface (α) of the resin layer of the pressure sensitive adhesive sheetproduced in Comparative Example 1.

INDUSTRIAL APPLICABILITY

One embodiment of the pressure sensitive adhesive sheet of the presentinvention is useful as a pressure sensitive adhesive sheet having alarge adhesive area that is used for identification or decoration, formasking in coating, and for surface protection for metal plates, etc.

REFERENCE SIGN LIST

-   1 a, 1 b, 2 a, 2 b Pressure Sensitive Adhesive Sheet-   11 Substrate-   12 Resin Layer-   12 a Surface (α)-   12 b Surface (β)-   (X) Resin Part (X)-   (Y) Particle Part (Y)-   (Xβ) Layer (Xβ) mainly containing the resin part (X)-   (Xα) Layer (Xα) mainly containing the resin part (X)-   (Y1) Fine particle-containing layer (Y1) containing the particle    part (Y) in an amount of 15% by mass or more-   13, 130, 131, 132 Concave portions-   13 a Cross Line-   14, 14 a Release Material-   50, 501, 502, 503, 504 Square having an edge length of 1 mm

1. A pressure sensitive adhesive sheet comprising, on a substrate or arelease material, a resin layer formed of a multilayer structure ofthree or more layers including a fine particle-containing layer thatcontains fine particles in an amount of 15% by mass or more, at least asurface (α) of the resin layer being opposite to the side thereof onwhich the substrate or the release material is provided having pressuresensitive adhesiveness, wherein the fine particle-containing layer isformed not as the outermost layer of the resin layer, and one or moreconcave portions exist on the surface (α) and the shapes of the one ormore concave portions have irregular shapes.
 2. The pressure sensitiveadhesive sheet according to claim 1, wherein the one or more concaveportions are formed through self-formation of the resin layer.
 3. Thepressure sensitive adhesive sheet according to claim 1, wherein, in thecross section in the thickness direction of the resin layer, theboundary between the fine particle-containing layer and the other layeris not parallel to the horizontal plane of the substrate or the releasematerial.
 4. The pressure sensitive adhesive sheet according to claim 1,wherein the one or more concave portions do not have a predeterminedpattern.
 5. The pressure sensitive adhesive sheet according to claim 1,wherein the plural concave portions exist on the surface (α).
 6. Thepressure sensitive adhesive sheet according to claim 5, wherein thepositions at which the plural concave portions exist have noperiodicity.
 7. The pressure sensitive adhesive sheet according to claim1, wherein the fine particle-containing layer includes, as existingtherein intermittently relative to the horizontal plane direction of thesubstrate or the release material, a part densely containing fineparticles and a part not containing fine particles.
 8. The pressuresensitive adhesive sheet according to claim 1, wherein the fineparticles are one or more selected from silica particles, metal oxideparticles and smectite.
 9. The pressure sensitive adhesive sheetaccording to claim 1, wherein the volume-average secondary particlediameter of the fine particles is 50 μm or less.
 10. (canceled)
 11. Thepressure sensitive adhesive sheet according to claim 1, wherein theother layer than the fine particle-containing layer is formed of acomposition containing a resin as a main component and having the fineparticles content of less than 15% by mass.
 12. The pressure sensitiveadhesive sheet according to claim 1, wherein the resin layer has amultilayer structure of, as laminated in this order, a layer (Xβ) mainlycontaining a resin part (X), a fine particle-containing layer (Y1)containing a particle part (Y) in an amount of 15% by mass or more, anda layer (Xα) mainly containing a resin part (X).
 13. (canceled)
 14. Thepressure sensitive adhesive sheet according to claim 12, wherein: thelayer (Xβ) is a layer formed of a composition (xα) containing a resin asa main component, the layer (Y1) is a layer formed of a composition (y)containing fine particles in an amount of 15% by mass or more, and thelayer (Xα) is a layer formed of a composition (xα) containing a resin asa main component.
 15. (canceled)
 16. A method for producing a pressuresensitive adhesive sheet according to claim 14, which comprises at leastthe following steps (1A) and (2A): step (1A): a step of forming, on asubstrate or a release material, a coating film (xβ′) formed by thecomposition (xβ) containing the resin as a main component, a coatingfilm (y′) formed by the composition (y) containing the fine particles inan amount of 15% by mass or more and a coating film (xα′) formed by thecomposition (xα) containing the resin as a main component, by laminatingin this order; and step (2A): a step of drying the coating film (xβ′),the coating film (y′) and the coating film (xα′) formed in the step (1A)simultaneously.
 17. A method for producing a pressure sensitive adhesivesheet according to claim 14, which comprises at least the followingsteps (1B) and (2B): step (1B): a step of forming, on a layer (Xβ)mainly containing a resin part (X) that is provided on a substrate or arelease material, a coating film (y′) formed by the composition (y)containing the fine particles in an amount of 15% by mass or more and acoating film (xα′) formed by the composition (xα) containing a resin asa main component, by laminating in this order; and step (2B): a step ofdrying the coating film (y′) and the coating film (xα′) formed in thestep (1B) simultaneously.
 18. A viscoelastic layer formed of amultilayer structure of 3 or more layers including a fineparticle-containing layer that contains fine particles, wherein: thefine particle-containing layer is formed not as the outermost layer ofthe viscoelastic layer, and one or more concave portions are formed onat least one surface of the viscoelastic layer, and the shapes of theone or more concave portions have irregular shapes.